Bug 2513477 (CVE-2026-68426)

Summary: CVE-2026-68426 kernel: xfrm: fix stale skb->prev after async crypto steals a GSO segment
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `xfrm` subsystem. 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.
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Description OSIDB Bzimport 2026-08-10 12:39:33 UTC 
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.
Comment 1 Mauro Matteo Cascella 2026-08-11 08:02:58 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081053-CVE-2026-68426-9cce@gregkh/T