High [CVE-2026-68426] fix stale skb->prev after async crypto steals a GSO segment

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix stale skb->prev after async crypto steals a GSO segment skb_gso_segment() leaves the segment list head with ->prev pointing at the last segment, an invariant validate_xmit_skb_list() relies on when it sets its tail pointer (tail = skb->prev).

When validate_xmit_xfrm() walks a GSO list and some segments are stolen by async crypto (->xmit() returns -EINPROGRESS), those segments are unlinked from the list but the head ->prev is never updated.

If the last segment is the one stolen, the returned head still has ->prev pointing at it, even though it is now owned by the crypto engine and may be freed. validate_xmit_skb_list() later does tail->next = skb, writing through that stale pointer -- a use-after-free. Repoint skb->prev at the last retained segment before returning.

This vulnerability arises when asynchronous cryptographic operations incorrectly handle network packet segments, leaving a pointer to memory that has already been released. An attacker could potentially exploit this use-after-free condition to cause a system crash (denial of service) or, in some scenarios, execute unauthorized code.

Red Hat severity: Important — CVSS 7.3 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H). Weakness: CWE-825.