# CVE-2026-99074: linux: In the Linux kernel, the following vulnerability has been resolved: ipv4: stop PMTU walk when nexthop group shrinks... CVE-2026-99074 is fixed in 19 products on 1 platform, first by DEBIAN-CVE-2026-99074, released October 24, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-99074 - Priority: High - CVSS: n/a (important) - EPSS: 0.0015 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Oct 23, 2026 ## 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.12 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | bpftool6.12-debuginfo amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel-livepatch-6.12.113-138.209 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo-common-aarch64 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo-common-x86_64 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-devel amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-headers amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-modules-extra amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-modules-extra-common amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-tools amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-tools-debuginfo amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | kernel6.12-tools-devel amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | linux Debian 13.5 (trixie) | 6.12.113-1 | [DEBIAN-CVE-2026-99074](https://patchblox.com/security/data/fix/linux/debian-cve-2026-99074.md) | Oct 24, 2026 | | Linux | linux Debian 14 | 7.2.11-1 | [DEBIAN-CVE-2026-99074](https://patchblox.com/security/data/fix/linux/debian-cve-2026-99074.md) | Oct 24, 2026 | | Linux | perf6.12 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | perf6.12-debuginfo amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | python3-perf6.12 amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | | Linux | python3-perf6.12-debuginfo amzn 2023 | 1:6.12.113-138.209.amzn2023 | [ALAS2023-2026-3335](https://patchblox.com/security/data/fix/linux/alas2023-2026-3335.md) | Nov 7, 2026 | --- Data as of 2026-11-08T19:12:23Z UTC. 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