UBUNTU-CVE-2026-80848

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UBUNTU-CVE-2026-80848

Summary:

Details: 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.

References: https://ubuntu.com/security/CVE-2026-80848, https://www.cve.org/CVERecord?id=CVE-2026-80848, https://git.kernel.org/linus/deb232e884877bf10b4ce2580909eedec986c284