NULL Pointer Dereference Affecting kernel6.12-debuginfo-common-aarch64 package, versions <1:6.12.113-138.209.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.15% (5th percentile)

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  • Snyk IDSNYK-AMZN2023-KERNEL612DEBUGINFOCOMMONAARCH64-21811183
  • published29 Oct 2026
  • disclosed23 Oct 2026

Introduced: 23 Oct 2026

NewCVE-2026-99074  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel6.12-debuginfo-common-aarch64 to version 1:6.12.113-138.209.amzn2023 or higher.
This issue was patched in ALAS2023-2026-3335.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel6.12-debuginfo-common-aarch64 package and not the kernel6.12-debuginfo-common-aarch64 package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1