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

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-21 · updated 2026-10-16

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.

Affected products

Linux kernel: from 5.10.84 before 5.10.265; from 5.15.7 before 5.15.216; from 5.4.164 before 5.5; 5.16 — fixed in 5.10.265, 5.15.216, 5.5, 7.2

How to fix

Upgrade to a fixed version: Linux kernel 5.10.265, 5.15.216, 5.5, 7.2. Check the vendor advisory for mitigations.

References

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