CVE-2026-68315

CVE-2026-68315 is a kernel panic bug in Linux SCTP stream reset handling. When a peer sends a stream reset request (IN), the kernel must generate a corresponding outbound response (OUT) — but these structures have different sizes: sctp_strreset_inreq is 8 bytes while sctp_strreset_outreq is 16 bytes. The kernel allocates memory based on the incoming request size, then attempts to construct a larger response, triggering a BUG() when the skb allocation fails. The vulnerability requires MTU exceeding 65535 bytes — which means IPv6 jumbogram support on loopback. This configuration is uncommon on internet-facing systems but appears in containerized environments, Kubernetes clusters with jumbo frames enabled, and HPC interconnects. The practical exploit surface is narrower than the CVSS 7.5 suggests, but when the conditions align, the result is an unauthenticated remote peer causing kernel panic via a standard socket operation. The patch corrects both directions: it rejects peer-initiated IN requests that would require an oversized OUT response, and it prevents the local setsockopt path from generating reset requests the peer cannot legally answer. This dual-direction fix signals the underlying problem wasn't a simple missing check — it was a code path asymmetry where neither side validated what the other side needed. For operators: verify whether SCTP runs over loopback or in environments with IPv6 jumbogram support. If so, prioritize the kernel update. If SCTP is used but these conditions don't apply, the vulnerability cannot trigger but should still be patched for defense-in-depth. Monitor for spikes in SCTP stream reset rejections, as the fix shifts the failure mode from kernel panic to application-level reset failure — a different denial-of-service surface that attackers may probe. The historical pattern matters: this is the third distinct stream reset vulnerability in a decade, suggesting the code path has accumulated structural weaknesses that single patches don't fully resolve.

Reviewed through automated stages and approved by a human before publication.