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CVE-2026-53012

nexthop: fix IPv6 route referencing IPv4 nexthop

publishedCWE-476

In the Linux kernel, the following vulnerability has been resolved: nexthop: fix IPv6 route referencing IPv4 nexthop syzbot reported a panic [1] [2]. When an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag of all groups containing this nexthop is not updated. This is because nh_group_v4_update is only called when replacing AF_INET to AF_INET6, but the reverse direction (AF_INET6 to AF_INET) is missed. This allows a stale has_v4=false to bypass fib6_check_nexthop, causing IPv6 routes to be attached to groups that effectively contain only AF_INET members. Subsequent route lookups then call nexthop_fib6_nh() which returns NULL for the AF_INET member, leading to a NULL pointer dereference. Fix by calling nh_group_v4_update whenever the family changes, not just AF_INET to AF_INET6. Reproducer: # AF_INET6 blackhole ip -6 nexthop add id 1 blackhole # group with has_v4=false ip nexthop add id 100 group 1 # replace with AF_INET (no -6), has_v4 stays false ip nexthop replace id 1 blackhole # pass stale has_v4 check ip -6 route add 2001:db8::/64 nhid 100 # panic ping -6 2001:db8::1 [1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0 [2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3

Technical severity5.5 mediumCVSS 3.1 · NVD: [email protected]

Published2026-06-24Source updated 2026-11-10

Collected2026-11-103 attributed sources

Fixes and workarounds

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Fix

The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.

Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
Linux Linux	≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < ceffe81a0be92afc0cd1340bc8ca46559cce9bb4 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < 9c2d6770a5f4545a307eb66979bef7656a34d621 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < 6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < aaac3bed034239e1d75732211d9b05f30b0b4f35 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < ad85961004fd4bd2f31209ac4b07612c6cefb9e7 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < 613c8f4a501421dd258b07ea614205d4e16ec845 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < b3b7e850e1541f0520c4a12ec884255c30427ff6 (affected, git) ≥ 7bf4796dd09984ad1612877a82d0d139c70ae27f; < 29c95185ba32b621fbc3800fb86e7dc3edf5c2be (affected, git) Other versions: unaffected	CNA: Linux
Linux Linux	5.3 (affected) ≥ 0; < 5.3 (unaffected, semver) ≥ 5.10.258; ≤ 5.10.* (unaffected, semver) ≥ 5.15.209; ≤ 5.15.* (unaffected, semver) ≥ 6.1.175; ≤ 6.1.* (unaffected, semver) ≥ 6.6.141; ≤ 6.6.* (unaffected, semver) ≥ 6.12.91; ≤ 6.12.* (unaffected, semver) ≥ 6.18.33; ≤ 6.18.* (unaffected, semver) ≥ 7.0.10; ≤ 7.0.* (unaffected, semver) ≥ 7.1; ≤ * (unaffected, original_commit_for_fix) Other versions: affected	CNA: Linux
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Siemens	≥ V3.1.6; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Siemens	≥ V3.1.6; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Siemens	≥ V3.1.6; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Siemens	≥ V3.1.6; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Siemens	≥ V3.1.6; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Siemens	≥ V3.1.7; < * (affected, custom) Other versions: unknown	ADP: siemens-SADP

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

NVD applicability configurations (1)

These expressions retain AND/OR operators, negation, and required environmental products. A listed product is not sufficient to establish exposure when additional conditions apply.

[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "5.10.258",
            "versionStartIncluding": "5.3",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "5.15.209",
            "versionStartIncluding": "5.11",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.1.175",
            "versionStartIncluding": "5.16",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.6.141",
            "versionStartIncluding": "6.2",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.12.91",
            "versionStartIncluding": "6.7",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "6.18.33",
            "versionStartIncluding": "6.13",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "7.0.10",
            "versionStartIncluding": "6.19",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
3.1 / 5.5 medium	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`	NVD: [email protected]

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://git.kernel.org/stable/c/ceffe81a0be92afc0cd1340bc8ca46559cce9bb4CNA: Linux
https://git.kernel.org/stable/c/9c2d6770a5f4545a307eb66979bef7656a34d621CNA: Linux
https://git.kernel.org/stable/c/6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8CNA: Linux
https://git.kernel.org/stable/c/aaac3bed034239e1d75732211d9b05f30b0b4f35CNA: Linux
https://git.kernel.org/stable/c/ad85961004fd4bd2f31209ac4b07612c6cefb9e7CNA: Linux
https://git.kernel.org/stable/c/613c8f4a501421dd258b07ea614205d4e16ec845CNA: Linux
https://git.kernel.org/stable/c/b3b7e850e1541f0520c4a12ec884255c30427ff6CNA: Linux
https://git.kernel.org/stable/c/29c95185ba32b621fbc3800fb86e7dc3edf5c2beCNA: Linux
https://cert-portal.siemens.com/productcert/html/ssa-019113.htmlADP: siemens-SADP
https://cert-portal.siemens.com/productcert/html/ssa-457936.htmlADP: siemens-SADP
https://git.kernel.org/stable/c/29c95185ba32b621fbc3800fb86e7dc3edf5c2be416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/613c8f4a501421dd258b07ea614205d4e16ec845416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/9c2d6770a5f4545a307eb66979bef7656a34d621416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/aaac3bed034239e1d75732211d9b05f30b0b4f35416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/ad85961004fd4bd2f31209ac4b07612c6cefb9e7416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/b3b7e850e1541f0520c4a12ec884255c30427ff6416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://git.kernel.org/stable/c/ceffe81a0be92afc0cd1340bc8ca46559cce9bb4416baaa9-dc9f-4396-8d5f-8c081fb06d67 · Patch
https://cert-portal.siemens.com/productcert/html/ssa-019113.html0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-457936.html0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

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