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ipv4: stop PMTU walk when nexthop group shrinks

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: ipv4: stop PMTU walk when nexthop group shrinks Commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") made __ip_rt_update_pmtu() update every path. For nexthop objects, fib_info_num_path() and fib_info_nhc() independently load nh->nh_grp. RCU protects each group's lifetime but does not make the loads observe the same group. If replacement shrinks the group after the loop accepts an index, fib_info_nhc() returns NULL and update_or_create_fnhe() dereferences it. A deterministic probe only widened the existing window between the real operations. On v7.2, an RTM_NEWNEXTHOP replacement published a one-member group after the PMTU reader accepted index 1 from a two-member group, producing: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: update_or_create_fnhe+0x45/0x15b0 Stop when the indexed path is absent. Groups are dense, so no later index exists in that snapshot. The same real-writer window completed 114,423 PMTU iterations without an oops with this check. A reproducer is available on request. Replacement requires CAP_NET_ADMIN in the network namespace. Where unprivileged user namespaces are permitted, a local user can obtain it in a new user and network namespace.

Announced Source revision 1
Original source ↗

CVE-2026-99074

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-2026-99074

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": "3bed2abab4a682d426624ce9add9d7b6d475d4e4",
        "lessThan": "7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7f5005457b3072fe1ddf15bfef869f2a1d98e05e",
        "lessThan": "c60d17d6dd61adc761ac6f65a008fefbc54cbf87",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
        "lessThan": "c6d670ac656badfd0e15355e07a13a6bdf3b69fd",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
        "lessThan": "f27483f9975b5065ff67054cc7eb8edac6083488",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
        "lessThan": "6619e01855e65ef35723685a557e3eb106f4ecf5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "fc07a232326a623d0be482e307c08ea7049c2846",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "6.6.79",
        "lessThan": "6.6.160",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.12.16",
        "lessThan": "6.12.113",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "5.15.179",
        "lessThan": "5.16",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.1.129",
        "lessThan": "6.2",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "net/ipv4/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": "6.13"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "6.13",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.160",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.113",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.57",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.11",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv4/route.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-99074

Source reference: /cveMetadata/cveId

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Event
#52898 · Revision 1
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