CVE-2026-31531 (GCVE-0-2026-31531)

Vulnerability from cvelistv5 – Published: 2026-04-23 11:12 – Updated: 2026-04-23 11:12
VLAI?
Title
ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()
Summary
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: <TASK> 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) </TASK> 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 currently limited and the command fails as follows: addattr_l ERROR: message exceeded bound of 1048
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 430a049190de3c9e219f43084de9f1122da04570 , < 615517f3f8d53b0cf41507c7599971e17adfdfa5 (git)
Affected: 430a049190de3c9e219f43084de9f1122da04570 , < 40bd39e383a0478fd5c221f393df05fd9d70cfbc (git)
Affected: 430a049190de3c9e219f43084de9f1122da04570 , < 635038fe19db391117e66b46bdc2b6e447ac801d (git)
Affected: 430a049190de3c9e219f43084de9f1122da04570 , < 14cf0cd35361f4e94824bf8a42f72713d7702a73 (git)
Create a notification for this product.
    Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 6.12.83 , ≤ 6.12.* (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "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": "615517f3f8d53b0cf41507c7599971e17adfdfa5",
              "status": "affected",
              "version": "430a049190de3c9e219f43084de9f1122da04570",
              "versionType": "git"
            },
            {
              "lessThan": "40bd39e383a0478fd5c221f393df05fd9d70cfbc",
              "status": "affected",
              "version": "430a049190de3c9e219f43084de9f1122da04570",
              "versionType": "git"
            },
            {
              "lessThan": "635038fe19db391117e66b46bdc2b6e447ac801d",
              "status": "affected",
              "version": "430a049190de3c9e219f43084de9f1122da04570",
              "versionType": "git"
            },
            {
              "lessThan": "14cf0cd35361f4e94824bf8a42f72713d7702a73",
              "status": "affected",
              "version": "430a049190de3c9e219f43084de9f1122da04570",
              "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": "5.3"
            },
            {
              "lessThan": "5.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.83",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.24",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.14",
              "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": "6.12.83",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.24",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.14",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()\n\nWhen querying a nexthop object via RTM_GETNEXTHOP, the kernel currently\nallocates a fixed-size skb using NLMSG_GOODSIZE. While sufficient for\nsingle nexthops and small Equal-Cost Multi-Path groups, this fixed\nallocation fails for large nexthop groups like 512 nexthops.\n\nThis results in the following warning splat:\n\n WARNING: net/ipv4/nexthop.c:3395 at rtm_get_nexthop+0x176/0x1c0, CPU#20: rep/4608\n [...]\n RIP: 0010:rtm_get_nexthop (net/ipv4/nexthop.c:3395)\n [...]\n Call Trace:\n  \u003cTASK\u003e\n  rtnetlink_rcv_msg (net/core/rtnetlink.c:6989)\n  netlink_rcv_skb (net/netlink/af_netlink.c:2550)\n  netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)\n  netlink_sendmsg (net/netlink/af_netlink.c:1894)\n  ____sys_sendmsg (net/socket.c:721 net/socket.c:736 net/socket.c:2585)\n  ___sys_sendmsg (net/socket.c:2641)\n  __sys_sendmsg (net/socket.c:2671)\n  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)\n  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n  \u003c/TASK\u003e\n\nFix this by allocating the size dynamically using nh_nlmsg_size() and\nusing nlmsg_new(), this is consistent with nexthop_notify() behavior. In\naddition, adjust nh_nlmsg_size_grp() so it calculates the size needed\nbased on flags passed. While at it, also add the size of NHA_FDB for\nnexthop group size calculation as it was missing too.\n\nThis cannot be reproduced via iproute2 as the group size is currently\nlimited and the command fails as follows:\n\naddattr_l ERROR: message exceeded bound of 1048"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-23T11:12:44.143Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/615517f3f8d53b0cf41507c7599971e17adfdfa5"
        },
        {
          "url": "https://git.kernel.org/stable/c/40bd39e383a0478fd5c221f393df05fd9d70cfbc"
        },
        {
          "url": "https://git.kernel.org/stable/c/635038fe19db391117e66b46bdc2b6e447ac801d"
        },
        {
          "url": "https://git.kernel.org/stable/c/14cf0cd35361f4e94824bf8a42f72713d7702a73"
        }
      ],
      "title": "ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31531",
    "datePublished": "2026-04-23T11:12:44.143Z",
    "dateReserved": "2026-03-09T15:48:24.112Z",
    "dateUpdated": "2026-04-23T11:12:44.143Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31531",
      "date": "2026-04-24",
      "epss": "0.0001",
      "percentile": "0.0117"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31531\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-23T12:17:01.820\",\"lastModified\":\"2026-04-23T16:17:41.280\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()\\n\\nWhen querying a nexthop object via RTM_GETNEXTHOP, the kernel currently\\nallocates a fixed-size skb using NLMSG_GOODSIZE. While sufficient for\\nsingle nexthops and small Equal-Cost Multi-Path groups, this fixed\\nallocation fails for large nexthop groups like 512 nexthops.\\n\\nThis results in the following warning splat:\\n\\n WARNING: net/ipv4/nexthop.c:3395 at rtm_get_nexthop+0x176/0x1c0, CPU#20: rep/4608\\n [...]\\n RIP: 0010:rtm_get_nexthop (net/ipv4/nexthop.c:3395)\\n [...]\\n Call Trace:\\n  \u003cTASK\u003e\\n  rtnetlink_rcv_msg (net/core/rtnetlink.c:6989)\\n  netlink_rcv_skb (net/netlink/af_netlink.c:2550)\\n  netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)\\n  netlink_sendmsg (net/netlink/af_netlink.c:1894)\\n  ____sys_sendmsg (net/socket.c:721 net/socket.c:736 net/socket.c:2585)\\n  ___sys_sendmsg (net/socket.c:2641)\\n  __sys_sendmsg (net/socket.c:2671)\\n  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)\\n  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\\n  \u003c/TASK\u003e\\n\\nFix this by allocating the size dynamically using nh_nlmsg_size() and\\nusing nlmsg_new(), this is consistent with nexthop_notify() behavior. In\\naddition, adjust nh_nlmsg_size_grp() so it calculates the size needed\\nbased on flags passed. While at it, also add the size of NHA_FDB for\\nnexthop group size calculation as it was missing too.\\n\\nThis cannot be reproduced via iproute2 as the group size is currently\\nlimited and the command fails as follows:\\n\\naddattr_l ERROR: message exceeded bound of 1048\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/14cf0cd35361f4e94824bf8a42f72713d7702a73\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/40bd39e383a0478fd5c221f393df05fd9d70cfbc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/615517f3f8d53b0cf41507c7599971e17adfdfa5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/635038fe19db391117e66b46bdc2b6e447ac801d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.