High [CVE-2026-74581] use-after-free in fib6_rule_suppress due to stale res->rt6 pointer
This high-severity Red Hat Linux advisory covers CVE-2026-74581 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
A use-after-free vulnerability was found in the Linux kernel's IPv6 FIB rule lookup path. In fib6_rule_suppress(), when a route is suppressed and released via ip6_rt_put_flags(), the res->rt6 pointer is not cleared.
If no later rule supplies a replacement route, fib6_rule_lookup() returns the stale (freed) rt6_info to its caller. The subsequent dst_release() then operates on freed memory, hitting rcuref_put_slowpath().
A local attacker who can configure IPv6 routing/FIB rules could trigger this to cause a denial of service (kernel crash) or potentially escalate privileges. Red Hat severity: Important — CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
Weakness: CWE-416. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9.
Will not fix / out of support: Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: kernel-rt.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 49 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 49 minutes ago·verify at source
Mitigation checklist
- To mitigate this issue, prevent the `ipv6` kernel module from loading. Create a file named `/etc/modprobe.d/disable-ipv6.conf` with the following content: ``` install ipv6 /bin/true blacklist ipv6 ``` After creating the file, regenerate the initramfs and reboot the system for the change to take effect. Applications or services that rely on the IPv6 protocol cannot use this mitigation and should prioritize applying the fix.
Official advisory · high-confidence parse· fetched 49 minutes ago·verify at source
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