ipv4: stop PMTU walk when nexthop group shrinks

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-99074
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:31 UTC
Updated2026-10-23 13:17:31 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 3bed2abab4a682d426624ce9add9d7b6d475d4e4 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a git Not specified
CNA Linux Linux affected 7f5005457b3072fe1ddf15bfef869f2a1d98e05e c60d17d6dd61adc761ac6f65a008fefbc54cbf87 git Not specified
CNA Linux Linux affected 7d3f3b4367f315a61fc615e3138f3d320da8c466 c6d670ac656badfd0e15355e07a13a6bdf3b69fd git Not specified
CNA Linux Linux affected 7d3f3b4367f315a61fc615e3138f3d320da8c466 f27483f9975b5065ff67054cc7eb8edac6083488 git Not specified
CNA Linux Linux affected 7d3f3b4367f315a61fc615e3138f3d320da8c466 6619e01855e65ef35723685a557e3eb106f4ecf5 git Not specified
CNA Linux Linux affected fc07a232326a623d0be482e307c08ea7049c2846 git Not specified
CNA Linux Linux affected b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e git Not specified
CNA Linux Linux affected 6.6.79 6.6.160 semver Not specified
CNA Linux Linux affected 6.12.16 6.12.113 semver Not specified
CNA Linux Linux affected 5.15.179 5.16 semver Not specified
CNA Linux Linux affected 6.1.129 6.2 semver Not specified
CNA Linux Linux affected 6.13 Not specified
CNA Linux Linux unaffected 6.13 semver Not specified
CNA Linux Linux unaffected 6.6.160 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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