CVE-2026-74581 net: ipv6: clear suppressed fib6 rule result

Critical 9.8 Published 21 Aug 2026 Updated 16 Oct 2026

A use-after-free in the Linux kernel IPv6 routing code allows attackers to cause a denial of service or potentially execute code via crafted network traffic.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-74581?

CVE-2026-74581 is a critical use after free vulnerability in Linux, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

net: ipv6: clear suppressed fib6 rule result

fib6_rule_suppress() drops a suppressed route with ip6_rt_put_flags(), but leaves res->rt6 pointing at the released rt6_info.

If no later rule supplies a replacement, fib6_rule_lookup() still sees res.rt6 and returns that stale dst to its caller. A suppressing rule can therefore leak a released route back to rt6_lookup(), and the next put hits rcuref_put_slowpath() from dst_release().

Clear res->rt6 when suppressing the route so suppressed lookups fall through to the null dst instead of reusing the released one.

Which versions are affected by CVE-2026-74581?

Linux distribution packages (40)

`bpftool` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`bpftool-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-abi-stablelists` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-core` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug-core` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug-devel` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug-modules` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debug-modules-extra` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-debuginfo-common-x86_64` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-devel` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-doc` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-modules` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-modules-extra` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-tools` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-tools-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`kernel-tools-libs` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`perf` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`perf-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`python3-perf` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`python3-perf-debuginfo` Red Hat:rhel_aus:8.4::baseos	All versions	`0:4.18.0-305.202.1.el8_4`
`bpftool` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`bpftool-debuginfo` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-abi-stablelists` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-core` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug-core` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug-debuginfo` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug-devel` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug-modules` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debug-modules-extra` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debuginfo` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-debuginfo-common-x86_64` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-devel` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-doc` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`
`kernel-modules` Red Hat:rhel_aus:8.6::baseos	All versions	`0:4.18.0-372.209.1.el8_6`

How do I fix CVE-2026-74581?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-74581 being exploited?

There is no known exploitation of CVE-2026-74581 in the wild and no public exploit code.

Sources

Also known as AZL-97001, BELL-CVE-2026-74581, DEBIAN-CVE-2026-74581, GHSA-7ph7-58w3-w755, RHSA-2026:59994, RHSA-2026:60437 and 3 more.