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ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop() When querying a nexthop object via RTM_GETNEXTHOP, the kernel currently allocates a fixed-size skb using NLMSG_GOODSIZE. While sufficient for single nexthops and small Equal-Cost Multi-Path groups, this fixed allocation fails for large nexthop groups like 512 nexthops. This results in the following warning splat: WARNING: net/ipv4/nexthop.c:3395 at rtm_get_nexthop+0x176/0x1c0, CPU#20: rep/4608 [...] RIP: 0010:rtm_get_nexthop (net/ipv4/nexthop.c:3395) [...] Call Trace: rtnetlink_rcv_msg (net/core/rtnetlink.c:6989) netlink_rcv_skb (net/netlink/af_netlink.c:2550) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) ____sys_sendmsg (net/socket.c:721 net/socket.c:736 net/socket.c:2585) ___sys_sendmsg (net/socket.c:2641) __sys_sendmsg (net/socket.c:2671) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Fix this by allocating the size dynamically using nh_nlmsg_size() and using nlmsg_new(), this is consistent with nexthop_notify() behavior. In addition, adjust nh_nlmsg_size_grp() so it calculates the size needed based on flags passed. While at it, also add the size of NHA_FDB for nexthop group size calculation as it was missing too. This cannot be reproduced via iproute2 as the group size is cu

Announced Source revision 1
Original source ↗

CVE-2026-31531

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-31531

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "430a049190de3c9e219f43084de9f1122da04570",
        "lessThan": "18a4543c1750f96be63e349936d2dfdcb360b2dc",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "430a049190de3c9e219f43084de9f1122da04570",
        "lessThan": "615517f3f8d53b0cf41507c7599971e17adfdfa5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "430a049190de3c9e219f43084de9f1122da04570",
        "lessThan": "40bd39e383a0478fd5c221f393df05fd9d70cfbc",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "430a049190de3c9e219f43084de9f1122da04570",
        "lessThan": "635038fe19db391117e66b46bdc2b6e447ac801d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "430a049190de3c9e219f43084de9f1122da04570",
        "lessThan": "14cf0cd35361f4e94824bf8a42f72713d7702a73",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv4/nexthop.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.3"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.3",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.160",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.83",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.24",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.14",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv4/nexthop.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-31531

Source reference: /cveMetadata/cveId

Publisher severity

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Event
#46134 · Revision 1
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