Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: ipv6: addrconf: fix temp address generation after prefix deprecation When a router temporarily deprecates an IPv6 prefix (either by sending a Router Advertisement with Preferred Lifetime = 0 or by letting the lifetime expire) and later restores it, the kernel permanently loses its ability to generate temporary privacy addresses (RFC 8981) for that prefix. This happens because the address worker attempts to generate a replacement temporary address when the current one nears expiration. As the base prefix is deprecated already, the generation fails after marking the temporary address as already having spawned a replacement (ifp->regen_count++). When the router eventually restores the prefix, the temporary address becomes active again. However, once it naturally expires, the address worker sees this temporary address already tried to generate one and skips the regeneration. Fix the issue by resetting the regen_count check of the latest temp address generated for the prefix updated by the incoming RA.

Affected versions

Linux: 76f793e3a47139d340185cbc1a314740c09b13d3 through before bff7b87dfa28a1502c18d0c6f1fadda5162fa854 (git); 76f793e3a47139d340185cbc1a314740c09b13d3 through before 4df5597c65446135362f72880995e8920f058fa0 (git); 76f793e3a47139d340185cbc1a314740c09b13d3 through before e20d8922aa8fe441d291364c96c2179a005b79ea (git); 3.2 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.