Bug 2528690 (CVE-2026-80848)

Summary: CVE-2026-80848 kernel: xfrm: espintcp: fix UAF during close
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the `xfrm: espintcp` component of the Linux kernel. A race condition exists during the closure of `espintcp` sockets, where a memory buffer (`skb`) can be freed while still being accessed by another process. This Use-After-Free (UAF) vulnerability could allow a local attacker to cause memory corruption, potentially leading to a denial of service or other unpredictable system behavior.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-04 16:24:16 UTC
In the Linux kernel, the following vulnerability has been resolved:

xfrm: espintcp: fix UAF during close

ZDI reported and analyzed a race condition during close for espintcp
sockets:

    espintcp_close() frees emsg->skb via kfree_skb() without holding
    any socket lock. Concurrently, the xfrm_trans_reinject work queue
    invokes esp_output_tcp_finish() -> espintcp_push_skb() ->
    espintcp_push_msgs() -> skb_send_sock_locked(), which reads the
    same skb as a data source.

Fix this by adding a synchronize_rcu() call after resetting sk_prot,
since esp_output_tcp_finish() runs under RCU and won't use a socket
with sk_prot == &tcp_prot.  Simply taking the socket lock in
espintcp_close() could lead to leaks, if esp_output_tcp_finish()
re-adds an skb in the slot we just freed. After this, the existing
barrier() is no longer needed.