Vulnerability-Lookup

CVE-2026-98374 (GCVE-0-2026-98374)

Vulnerability from cvelistv5 – Published: 2026-10-07 13:01 – Updated: 2026-10-07 13:01

Title

tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()

Summary

In the Linux kernel, the following vulnerability has been resolved: tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack() When tcp_send_synack() replaces the cloned SYN skb at the head of the retransmit queue with a copy, it frees the original with tcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack. tp->retransmit_skb_hint keeps pointing at the freed skbuff_fclone_cache object. The dangling hint is read in tcp_verify_retransmit_hint() and used as the root of the rbtree walk in tcp_xmit_retransmit_queue(). An unprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with an attacker-supplied ICMP fragmentation-needed message, after which a simultaneous open frees the armed SYN skb: BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) Read of size 4 at addr ffff88800604d928 by task swapper/1/0 Call Trace: tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) tcp_simple_retransmit (net/ipv4/tcp_input.c:3158) tcp_v4_err (net/ipv4/tcp_ipv4.c:587) Sync the hint to the copy.

Severity

No CVSS data available.

Assigner

Linux mitre root Scorecard

References

7 references

URL	Tags
https://git.kernel.org/stable/c/fad6d429651e74836…
https://git.kernel.org/stable/c/c5b4da1f403a658c1…
https://git.kernel.org/stable/c/71d45049b0d631dfd…
https://git.kernel.org/stable/c/e3ea71cb1408a013e…
https://git.kernel.org/stable/c/631aa4cb45099f09e…
https://git.kernel.org/stable/c/0f87720c7e4bcab07…
https://git.kernel.org/stable/c/fe99bbeee5c5dbd3a…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < fad6d429651e748365e93ca54645accc212f0018 (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < c5b4da1f403a658c1c19766be2b426003ada419f (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < 71d45049b0d631dfdbf3c65305f7fca676de023b (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < e3ea71cb1408a013ed4e8a757b815f1a919324bd (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < 631aa4cb45099f09e9385dd786bd291c6270bfc4 (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < 0f87720c7e4bcab07c24888b3cf12bfe857bb90e (git) Affected: c31b70c9968fe9c4194d1b5d06d07596a3b680de , < fe99bbeee5c5dbd3abc30721a8079ced59649d97 (git)	guessed
Linux	Linux	Affected: 5.11 Unaffected: 0 , < 5.11 (semver) Unaffected: 5.15.222 , ≤ 5.15.* (semver) Unaffected: 6.1.189 , ≤ 6.1.* (semver) Unaffected: 6.6.158 , ≤ 6.6.* (semver) Unaffected: 6.12.112 , ≤ 6.12.* (semver) Unaffected: 6.18.55 , ≤ 6.18.* (semver) Unaffected: 7.2.9 , ≤ 7.2.* (semver) Unaffected: 7.3-rc5 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "fad6d429651e748365e93ca54645accc212f0018",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "c5b4da1f403a658c1c19766be2b426003ada419f",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "71d45049b0d631dfdbf3c65305f7fca676de023b",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "e3ea71cb1408a013ed4e8a757b815f1a919324bd",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "631aa4cb45099f09e9385dd786bd291c6270bfc4",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "0f87720c7e4bcab07c24888b3cf12bfe857bb90e",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
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              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.11"
            },
            {
              "lessThan": "5.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.55",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.222",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.189",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.158",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.112",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.55",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.9",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc5",
                  "versionStartIncluding": "5.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp-\u003ehighest_sack.\ntp-\u003eretransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-07T13:01:48.600Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"
        },
        {
          "url": "https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"
        },
        {
          "url": "https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"
        },
        {
          "url": "https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"
        },
        {
          "url": "https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"
        },
        {
          "url": "https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"
        },
        {
          "url": "https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"
        }
      ],
      "title": "tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98374",
    "datePublished": "2026-10-07T13:01:48.600Z",
    "dateReserved": "2026-09-25T10:25:14.345Z",
    "dateUpdated": "2026-10-07T13:01:48.600Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv4/tcp_output.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "fad6d429651e748365e93ca54645accc212f0018",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "c5b4da1f403a658c1c19766be2b426003ada419f",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "71d45049b0d631dfdbf3c65305f7fca676de023b",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "e3ea71cb1408a013ed4e8a757b815f1a919324bd",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "631aa4cb45099f09e9385dd786bd291c6270bfc4",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "0f87720c7e4bcab07c24888b3cf12bfe857bb90e",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "fe99bbeee5c5dbd3abc30721a8079ced59649d97",
                    "status": "affected",
                    "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
                    "versionType": "git"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv4/tcp_output.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "5.11"
                  },
                  {
                    "lessThan": "5.11",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "5.15.*",
                    "status": "unaffected",
                    "version": "5.15.222",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.1.*",
                    "status": "unaffected",
                    "version": "6.1.189",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.6.*",
                    "status": "unaffected",
                    "version": "6.6.158",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.12.*",
                    "status": "unaffected",
                    "version": "6.12.112",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.18.*",
                    "status": "unaffected",
                    "version": "6.18.55",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.2.*",
                    "status": "unaffected",
                    "version": "7.2.9",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.3-rc5",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp-\u003ehighest_sack.\ntp-\u003eretransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy."
          }
        ],
        "id": "CVE-2026-98374",
        "lastModified": "2026-10-07T13:17:23.023",
        "metrics": {},
        "published": "2026-10-07T13:17:23.023",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}

FKIE_CVE-2026-98374

Vulnerability from fkie_nvd - Published: 2026-10-07 13:17 - Updated: 2026-10-07 13:17

Severity

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "fad6d429651e748365e93ca54645accc212f0018",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "c5b4da1f403a658c1c19766be2b426003ada419f",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "71d45049b0d631dfdbf3c65305f7fca676de023b",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "e3ea71cb1408a013ed4e8a757b815f1a919324bd",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "631aa4cb45099f09e9385dd786bd291c6270bfc4",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "0f87720c7e4bcab07c24888b3cf12bfe857bb90e",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            },
            {
              "lessThan": "fe99bbeee5c5dbd3abc30721a8079ced59649d97",
              "status": "affected",
              "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.11"
            },
            {
              "lessThan": "5.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.55",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp-\u003ehighest_sack.\ntp-\u003eretransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy."
    }
  ],
  "id": "CVE-2026-98374",
  "lastModified": "2026-10-07T13:17:23.023",
  "metrics": {},
  "published": "2026-10-07T13:17:23.023",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-2Q84-VC4J-MP23

Vulnerability from github – Published: 2026-10-07 15:31 – Updated: 2026-10-07 15:31

Details

In the Linux kernel, the following vulnerability has been resolved:

tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()

When tcp_send_synack() replaces the cloned SYN skb at the head of the retransmit queue with a copy, it frees the original with tcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack. tp->retransmit_skb_hint keeps pointing at the freed skbuff_fclone_cache object.

The dangling hint is read in tcp_verify_retransmit_hint() and used as the root of the rbtree walk in tcp_xmit_retransmit_queue(). An unprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with an attacker-supplied ICMP fragmentation-needed message, after which a simultaneous open frees the armed SYN skb:

BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) Read of size 4 at addr ffff88800604d928 by task swapper/1/0 Call Trace: tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) tcp_simple_retransmit (net/ipv4/tcp_input.c:3158) tcp_v4_err (net/ipv4/tcp_ipv4.c:587)

Sync the hint to the copy.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-98374"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-07T13:17:23Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp-\u003ehighest_sack.\ntp-\u003eretransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy.",
  "id": "GHSA-2q84-vc4j-mp23",
  "modified": "2026-10-07T15:31:59Z",
  "published": "2026-10-07T15:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98374"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-98374 (GCVE-0-2026-98374)

FKIE_CVE-2026-98374

GHSA-2Q84-VC4J-MP23

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