CVE-2026-99074
ipv4: stop PMTU walk when nexthop group shrinks
No known exploitation. No EPSS score yet. Fixed versions are out.
What to do
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- LinuxAffected: ≥ 3bed2abab4a682d426624ce9add9d7b6d475d4e4, < 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4aUpgrade to: 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4aAffected: ≥ 7f5005457b3072fe1ddf15bfef869f2a1d98e05e, < c60d17d6dd61adc761ac6f65a008fefbc54cbf87Upgrade to: c60d17d6dd61adc761ac6f65a008fefbc54cbf87Affected: ≥ 7d3f3b4367f315a61fc615e3138f3d320da8c466, < c6d670ac656badfd0e15355e07a13a6bdf3b69fdUpgrade to: c6d670ac656badfd0e15355e07a13a6bdf3b69fdAffected: ≥ 7d3f3b4367f315a61fc615e3138f3d320da8c466, < f27483f9975b5065ff67054cc7eb8edac6083488Upgrade to: f27483f9975b5065ff67054cc7eb8edac6083488 + 7 more branchesStated by: CVE record
Versions as the sources state them. Full version matrix after sign-in
What it is
From the CVE 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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
No EPSS score yet. New CVEs are usually scored within a few days.
Lifecycle
2 events over 0 days, from the signal feeds we watch.
- Publishedrecord updated
Affected products
Sources
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