CVE-2026-43374 (GCVE-0-2026-43374)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-10-19 19:16
VLAI
Title
net: nexthop: fix percpu use-after-free in remove_nh_grp_entry
Summary
In the Linux kernel, the following vulnerability has been resolved: net: nexthop: fix percpu use-after-free in remove_nh_grp_entry When removing a nexthop from a group, remove_nh_grp_entry() publishes the new group via rcu_assign_pointer() then immediately frees the removed entry's percpu stats with free_percpu(). However, the synchronize_net() grace period in the caller remove_nexthop_from_groups() runs after the free. RCU readers that entered before the publish still see the old group and can dereference the freed stats via nh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a use-after-free on percpu memory. Fix by deferring the free_percpu() until after synchronize_net() in the caller. Removed entries are chained via nh_list onto a local deferred free list. After the grace period completes and all RCU readers have finished, the percpu stats are safely freed.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:16 UTC
CWE
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f4676ea74b8549cd88dbfe2a592ce4530039e61f , < abf4feaee6405f1441929c6ebe7a250f2cd170a7 (git)
Affected: f4676ea74b8549cd88dbfe2a592ce4530039e61f , < ab5ebab9664214ba41a7633cb4e72f128204f924 (git)
Affected: f4676ea74b8549cd88dbfe2a592ce4530039e61f , < 9e08ad731862b22a87cc55f752e16d66cdc9e231 (git)
Affected: f4676ea74b8549cd88dbfe2a592ce4530039e61f , < b2662e7593e94ae09b1cf7ee5f09160a3612bcb2 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.19 , ≤ 6.18.* (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/ipv4/nexthop.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "abf4feaee6405f1441929c6ebe7a250f2cd170a7",
                  "status": "affected",
                  "version": "f4676ea74b8549cd88dbfe2a592ce4530039e61f",
                  "versionType": "git"
                },
                {
                  "lessThan": "ab5ebab9664214ba41a7633cb4e72f128204f924",
                  "status": "affected",
                  "version": "f4676ea74b8549cd88dbfe2a592ce4530039e61f",
                  "versionType": "git"
                },
                {
                  "lessThan": "9e08ad731862b22a87cc55f752e16d66cdc9e231",
                  "status": "affected",
                  "version": "f4676ea74b8549cd88dbfe2a592ce4530039e61f",
                  "versionType": "git"
                },
                {
                  "lessThan": "b2662e7593e94ae09b1cf7ee5f09160a3612bcb2",
                  "status": "affected",
                  "version": "f4676ea74b8549cd88dbfe2a592ce4530039e61f",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "net/ipv4/nexthop.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "6.9"
                },
                {
                  "lessThan": "6.9",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.78",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.19",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.19.*",
                  "status": "unaffected",
                  "version": "6.19.9",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.0",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.78",
                      "versionStartIncluding": "6.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.18.19",
                      "versionStartIncluding": "6.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.19.9",
                      "versionStartIncluding": "6.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.0",
                      "versionStartIncluding": "6.9",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: nexthop: fix percpu use-after-free in remove_nh_grp_entry\n\nWhen removing a nexthop from a group, remove_nh_grp_entry() publishes\nthe new group via rcu_assign_pointer() then immediately frees the\nremoved entry\u0027s percpu stats with free_percpu(). However, the\nsynchronize_net() grace period in the caller remove_nexthop_from_groups()\nruns after the free. RCU readers that entered before the publish still\nsee the old group and can dereference the freed stats via\nnh_grp_entry_stats_inc() -\u003e get_cpu_ptr(nhge-\u003estats), causing a\nuse-after-free on percpu memory.\n\nFix by deferring the free_percpu() until after synchronize_net() in the\ncaller. Removed entries are chained via nh_list onto a local deferred\nfree list. After the grace period completes and all RCU readers have\nfinished, the percpu stats are safely freed."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The freeing side is reached through `RTM_DELNEXTHOP` over rtnetlink, which is a local netlink configuration interface. Remote packets can hit the RCU read side, but an attacker must locally trigger nexthop deletion to create the UAF.\nAC:L - A local attacker can create nexthop groups, attach routes, generate concurrent route lookups, and delete a member nexthop, controlling both sides of the race. The bug is a straightforward RCU grace-period violation rather than a condition dependent on external state.\nPR:L - The rtnetlink non-GET path requires `CAP_NET_ADMIN` in the socket\u0027s network namespace. Because this is reachable with namespaced `CAP_NET_ADMIN` via user/network namespaces on affected systems, this is Low rather than High.\nUI:N - No victim interaction is required once the attacker has local access and the needed namespace capability. The attacker can perform the netlink operations and traffic generation directly.\nS:U - The vulnerability corrupts kernel memory within the same kernel security authority. It is a kernel privilege-impact bug, not a VM escape or cross-scope boundary bypass.\nC:H - This is a use-after-free of per-CPU nexthop group statistics reachable from RCU route readers. Following kernel CVSS guidance, UAF memory corruption is treated as enabling high confidentiality impact.\nI:H - The stale reader writes packet counters and sequence state through a freed per-CPU pointer, creating memory corruption that can plausibly be shaped into write/control-flow impact. Per the required guidance, UAF is scored as High integrity impact.\nA:H - The stale dereference of freed per-CPU memory can crash or otherwise destabilize the kernel. Any kernel UAF with crash potential is High availability impact."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T12:27:34.663Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7"
            },
            {
              "url": "https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924"
            },
            {
              "url": "https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231"
            },
            {
              "url": "https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2"
            }
          ],
          "title": "net: nexthop: fix percpu use-after-free in remove_nh_grp_entry",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-43374",
        "datePublished": "2026-05-08T14:21:24.537Z",
        "dateReserved": "2026-05-01T14:12:56.006Z",
        "dateUpdated": "2026-10-19T19:16:28.049Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

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Vulnerability timeline

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