CVE-2026-74562 (GCVE-0-2026-74562)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:28 – Updated: 2026-08-17 05:48
VLAI
Title
nexthop: take nh->lock for f6i_list walks in replace check and notify
Summary
In the Linux kernel, the following vulnerability has been resolved: nexthop: take nh->lock for f6i_list walks in replace check and notify fib6_check_nh_list() and __nexthop_replace_notify() walk nh->f6i_list during an RTNL-serialized nexthop replace without holding nh->lock. IPv6 RTM_NEWROUTE/RTM_DELROUTE run without RTNL and mutate that list under nh->lock (fib6_add_rt2node_nh(), fib6_purge_rt()), so both walks race a concurrent route delete that unlinks and frees a fib6_info: BUG: KASAN: slab-use-after-free in rt6_fill_node.isra.0 (net/ipv6/route.c:5799) Read of size 4 at addr ffff888014607e64 by task exploit/143 rt6_fill_node.isra.0 (net/ipv6/route.c:5799) fib6_rt_update (net/ipv6/route.c:6412) __nexthop_replace_notify (net/ipv4/nexthop.c:2542) rtm_new_nexthop (net/ipv4/nexthop.c:2554) rtnetlink_rcv_msg (net/core/rtnetlink.c:7076) BUG: KASAN: slab-use-after-free in fib6_check_nh_list (net/ipv4/nexthop.c:1605) Read of size 8 at addr ffff888014a7d068 by task exploit/142 fib6_check_nh_list (net/ipv4/nexthop.c:1605) rtm_new_nexthop (net/ipv4/nexthop.c:2575) rtnetlink_rcv_msg (net/core/rtnetlink.c:7076) Both walks only read the entries and take no tb6_lock, so protect them with nh->lock; fib6_rt_update() uses gfp_any(), which returns GFP_ATOMIC under the lock.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 081efd18326e353c6fbfdeff903a83edde953f72 , < bb2b072c619c1f741a6234257050f72005dc63ef (git)
Affected: 081efd18326e353c6fbfdeff903a83edde953f72 , < 072cd1f21819dedd2252e704d255de3b0cfc61a7 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "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": "bb2b072c619c1f741a6234257050f72005dc63ef",
              "status": "affected",
              "version": "081efd18326e353c6fbfdeff903a83edde953f72",
              "versionType": "git"
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              "versionType": "git"
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          "product": "Linux",
          "programFiles": [
            "net/ipv4/nexthop.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.8",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: take nh-\u003elock for f6i_list walks in replace check and notify\n\nfib6_check_nh_list() and __nexthop_replace_notify() walk nh-\u003ef6i_list\nduring an RTNL-serialized nexthop replace without holding nh-\u003elock. IPv6\nRTM_NEWROUTE/RTM_DELROUTE run without RTNL and mutate that list under\nnh-\u003elock (fib6_add_rt2node_nh(), fib6_purge_rt()), so both walks race a\nconcurrent route delete that unlinks and frees a fib6_info:\n\n  BUG: KASAN: slab-use-after-free in rt6_fill_node.isra.0 (net/ipv6/route.c:5799)\n  Read of size 4 at addr ffff888014607e64 by task exploit/143\n   rt6_fill_node.isra.0 (net/ipv6/route.c:5799)\n   fib6_rt_update (net/ipv6/route.c:6412)\n   __nexthop_replace_notify (net/ipv4/nexthop.c:2542)\n   rtm_new_nexthop (net/ipv4/nexthop.c:2554)\n   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\n  BUG: KASAN: slab-use-after-free in fib6_check_nh_list (net/ipv4/nexthop.c:1605)\n  Read of size 8 at addr ffff888014a7d068 by task exploit/142\n   fib6_check_nh_list (net/ipv4/nexthop.c:1605)\n   rtm_new_nexthop (net/ipv4/nexthop.c:2575)\n   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\nBoth walks only read the entries and take no tb6_lock, so protect them\nwith nh-\u003elock; fib6_rt_update() uses gfp_any(), which returns GFP_ATOMIC\nunder the lock."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only via local RTNETLINK messages (RTM_NEWNEXTHOP replace and concurrent RTM_NEWROUTE/RTM_DELROUTE) sent on AF_NETLINK sockets, not by processing remote network packets.\nAC:L - An attacker can reliably trigger the race by running concurrent netlink threads that replace a nexthop while deleting IPv6 routes bound to it; both sides of the race are attacker-controlled, as demonstrated by the reported KASAN reproducers.\nPR:L - All vulnerable rtnetlink handlers require CAP_NET_ADMIN via netlink_net_capable(), which unprivileged local users can obtain inside a user/network namespace (unshare -Urn), not only real init-namespace root.\nUI:N - Exploitation requires no victim interaction beyond the attacker issuing coordinated netlink configuration commands from local processes.\nS:C - A successful UAF from CAP_NET_ADMIN inside a user/network namespace can corrupt host kernel memory and escape the container sandbox to compromise the host system.\nC:H - The race performs use-after-free reads of freed fib6_info objects (e.g., fib6_src and fib6_flags in fib6_check_nh_list and rt6_fill_node), enabling arbitrary kernel memory disclosure via heap reuse.\nI:H - Slab UAF on fib6_info during nexthop replace notification can be leveraged with heap spraying for arbitrary kernel writes and local privilege escalation to host root.\nA:H - The bug provably causes slab-use-after-free kernel oops (KASAN) during route notification and can panic or hang the system when triggered repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:48:41.938Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bb2b072c619c1f741a6234257050f72005dc63ef"
        },
        {
          "url": "https://git.kernel.org/stable/c/072cd1f21819dedd2252e704d255de3b0cfc61a7"
        }
      ],
      "title": "nexthop: take nh-\u003elock for f6i_list walks in replace check and notify",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74562",
    "datePublished": "2026-08-15T12:28:05.154Z",
    "dateReserved": "2026-08-15T05:44:03.916Z",
    "dateUpdated": "2026-08-17T05:48:41.938Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-74562",
      "date": "2026-10-02",
      "epss": "0.00165",
      "percentile": "0.05167"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "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": [
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                    "version": "081efd18326e353c6fbfdeff903a83edde953f72",
                    "versionType": "git"
                  },
                  {
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                    "versionType": "git"
                  }
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              },
              {
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                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "6.16"
                  },
                  {
                    "lessThan": "6.16",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
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                    "status": "unaffected",
                    "version": "7.1.8",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.2",
                    "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\nnexthop: take nh-\u003elock for f6i_list walks in replace check and notify\n\nfib6_check_nh_list() and __nexthop_replace_notify() walk nh-\u003ef6i_list\nduring an RTNL-serialized nexthop replace without holding nh-\u003elock. IPv6\nRTM_NEWROUTE/RTM_DELROUTE run without RTNL and mutate that list under\nnh-\u003elock (fib6_add_rt2node_nh(), fib6_purge_rt()), so both walks race a\nconcurrent route delete that unlinks and frees a fib6_info:\n\n  BUG: KASAN: slab-use-after-free in rt6_fill_node.isra.0 (net/ipv6/route.c:5799)\n  Read of size 4 at addr ffff888014607e64 by task exploit/143\n   rt6_fill_node.isra.0 (net/ipv6/route.c:5799)\n   fib6_rt_update (net/ipv6/route.c:6412)\n   __nexthop_replace_notify (net/ipv4/nexthop.c:2542)\n   rtm_new_nexthop (net/ipv4/nexthop.c:2554)\n   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\n  BUG: KASAN: slab-use-after-free in fib6_check_nh_list (net/ipv4/nexthop.c:1605)\n  Read of size 8 at addr ffff888014a7d068 by task exploit/142\n   fib6_check_nh_list (net/ipv4/nexthop.c:1605)\n   rtm_new_nexthop (net/ipv4/nexthop.c:2575)\n   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\nBoth walks only read the entries and take no tb6_lock, so protect them\nwith nh-\u003elock; fib6_rt_update() uses gfp_any(), which returns GFP_ATOMIC\nunder the lock."
          }
        ],
        "id": "CVE-2026-74562",
        "lastModified": "2026-08-17T06:19:54.303",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "CHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.0,
              "impactScore": 6.0,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-08-15T13:18:01.690",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/072cd1f21819dedd2252e704d255de3b0cfc61a7"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/bb2b072c619c1f741a6234257050f72005dc63ef"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T14:19:49+00:00",
      "cve": "CVE-2026-74562",
      "id": "CVE-2026-74562",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nexthop: take nh-\u003elock for f6i_list walks in replace check and notify",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74562.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-08-18T16:53:43Z",
      "cve": "CVE-2026-74562",
      "id": "CVE-2026-74562",
      "initial_release_date": "2026-08-15T23:50:10Z",
      "product_status:known_not_affected": "284",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74562",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74562.json",
      "version": "4"
    }
  }
}



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