CVE-2026-64551

Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source

AV:NAttack vector, network

The vulnerable code is in the SCTP receive-side state machine and is driven entirely by an attacker-crafted ERROR chunk arriving over the network; no local access is needed. Per kernel guidance, net/ stack bugs reachable via received packets (SCTP explicitly) are Network.

AC:LAttack complexity, low

The attacker fully controls the trigger: acting as the SCTP peer it answers INIT with INIT-ACK to place the association in COOKIE_ECHOED, then sends a minimal ERROR chunk with a 4-byte STALE_COOKIE cause as the last chunk in the packet. There is no race, no memory-layout dependency, and the vtag needed is the one the victim itself advertised in its INIT.

PR:NPrivileges required, none

SCTP association setup is unauthenticated; the only check is sctp_vtag_verify() against a tag the peer already received in the victim's INIT. The attacker needs no credentials or privileges on the target system.

UI:NUser interaction, none

No human user action is required — SCTP client daemons (SIGTRAN, Diameter, cluster transports) establish and retry associations automatically, and an on-path attacker can inject the ERROR into an in-progress handshake. In the local variant an unprivileged process creates both sides itself with no user involved.

S:UScope, unchanged

The out-of-bounds read and the resulting disclosure stay within the kernel's own security authority; no VM, sandbox, or IOMMU boundary is crossed.

C:HConfidentiality impact, high

Uninitialized kernel memory past skb->tail is read and then transmitted straight back to the attacker inside the reply INIT's Cookie Preservative parameter, and the attack can be repeated indefinitely to sample recycled network-buffer memory that may contain remnants of other connections' traffic. This is a remote, unauthenticated, repeatable kernel heap disclosure oracle, matching the C:H treatment given to the sibling SCTP uninit-read CVE-2026-53225.

I:NIntegrity impact, none

The bug is a pure read; nothing in kernel memory or in the victim's association state is modified. The only affected value is a protocol field in a packet sent to the attacker itself.

A:HAvailability impact, high

The read runs past the end of the received packet data, a memory-safety violation whose target is not proven to remain inside the skb's allocation across all receive paths (GSO/frag_list segments, UDP-encapsulated and linearized skbs), so it can fault and oops; kernel guidance and the CNA's scoring of the equivalent SCTP out-of-bounds-read bug both treat this class as A:H.