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net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics. Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows: 1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change. 2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless. 3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_p

Announced Source revision 1
Original source ↗

CVE-2026-23300

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-2026-23300

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": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "607e68c1b7c5a30c795571be1906d716e989a644",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "c11d7c56c2076ee9cd72004f1976fe0734df2ae9",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "b299121e7453d23faddf464087dff513a495b4fc",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "f7c9f8e3607440fe39300efbaf46cf7b5eecb23f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "b3b5a037d520afe3d5276e653bc0ff516bbda34c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "8650db85b4259d2885d2a80fbc2317ce24194133",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
        "lessThan": "21ec92774d1536f71bdc90b0e3d052eff99cf093",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv6/route.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": "5.10.253",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.203",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.167",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.130",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.77",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.17",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.7",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv6/route.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-23300

Source reference: /cveMetadata/cveId

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No explicit severity was provided.

Event
#27218 · Revision 1
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