CVE-2026-98549
In the Linux kernel, the following vulnerability has been resolved: tcp: prevent collapsing skbs…
- Risk score
- 70/100
- CVSS
- 9.1 v3.1
- Exploit chance (30 days)
- 0.1%
- Published
- 18 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- A critical vulnerability in the Linux kernel's TCP implementation allows an attacker to potentially access sensitive data. An attacker could exploit this vulnerability to access sensitive data.
- Affected
- {'products': ['Linux kernel'], 'packages': [], 'versions': []}
- Fix
- Check the linked advisory for details on the fix
- Exploitation
- No known exploitation
Why it is Amber
- CVSS 9.1 critical
- Remotely exploitable without logging in
- On your watchlist: linux kernel
References
- https://git.kernel.org/stable/c/08e835f5ec6e261c79d8c39f8618b3af29e3b0da
- https://git.kernel.org/stable/c/1ae7aee395245874d797890380d9192bd858fb7e
- https://git.kernel.org/stable/c/7ba87509c54cd519e7ed362e0c85e8431f066a18
- https://git.kernel.org/stable/c/9e2a2f98e8c0197108c6d97a1fa43bfd89071c30
- https://git.kernel.org/stable/c/fc6d80eb504458d6416b75a94188b268c95c6533
Original description
In the Linux kernel, the following vulnerability has been resolved: tcp: prevent collapsing skbs across boundary in rtx queue tcp_write_collapse_fence() sets TCP_SKB_CB(skb)->eor = 1 on tcp_write_queue_tail(sk) to prevent skbs queued after a switch to device encryption from being collapsed into earlier skbs. The fence is a no-op if all earlier data has already been transmitted when the switch happens: sk->sk_write_queue is empty. The not yet acknowledged earlier skbs wait in sk->tcp_rtx_queue with eor 0. On a subsequent retransmit or SACK shift, tcp_retrans_try_collapse() or tcp_shift_skb_data() can then merge an skb queued after the switch into one queued before it. Both users of the fence are affected: - psp: devices only encrypt skbs with skb->decrypted set. The merged skb keeps decrypted = 0 from the earlier skb, so merged data sent after psp_sock_assoc_set_tx() is retransmitted in cleartext. - tls device offload: the merged skb straddles the start marker set in tls_set_device_offload(). The software fallback (fill_sg_in() returns -EINVAL) and the mlx5, nfp and funeth drivers cannot handle such an skb and drop it. Every retransmit rebuilds the same skb, so the connection stalls. Fix this in two places, for defense in depth: 1. Fall back to tcp_rtx_queue_tail(sk) in tcp_write_collapse_fence() when tcp_write_queue_tail(sk) is NULL. 2. Check !skb_cmp_decrypted(to, from) in tcp_skb_can_collapse(), as tcp_skb_can_collapse_rx() does on receive. skb_shift(), which both collapse paths call, already has a DEBUG_NET_WARN_ON_ONCE() for this condition.
Last activity 18 Oct 2026. Patch Forecast updates every hour.