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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-99074

ipv4: stop PMTU walk when nexthop group shrinks

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 3bed2abab4a682d426624ce9add9d7b6d475d4e4 to < 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4aaffected
  • 7f5005457b3072fe1ddf15bfef869f2a1d98e05e to < c60d17d6dd61adc761ac6f65a008fefbc54cbf87affected
  • 7d3f3b4367f315a61fc615e3138f3d320da8c466 to < c6d670ac656badfd0e15355e07a13a6bdf3b69fdaffected
  • 7d3f3b4367f315a61fc615e3138f3d320da8c466 to < f27483f9975b5065ff67054cc7eb8edac6083488affected
  • 7d3f3b4367f315a61fc615e3138f3d320da8c466 to < 6619e01855e65ef35723685a557e3eb106f4ecf5affected
  • fc07a232326a623d0be482e307c08ea7049c2846affected
  • b1f7bdee5750d6cbb9497140cd6582abc5fdcb9eaffected
  • 6.6.79 to < 6.6.160affected
  • 6.12.16 to < 6.12.113affected
  • 5.15.179 to < 5.16affected
  • 6.1.129 to < 6.2affected

Linux Linux

Default version status: affected

  • 6.13affected
  • 0 to < 6.13unaffected
  • 6.6.160 to ≤ 6.6.*unaffected
  • 6.12.113 to ≤ 6.12.*unaffected
  • 6.18.57 to ≤ 6.18.*unaffected
  • 7.2.11 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References