CVE-2026-98549

CRITICALCVSS 9.1/10EPSS 0.39%

Last modified

CVE-2026-98549 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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. EPSS estimates a 0.39% chance of exploitation in the next 30 days.

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.

Metrics

EPSS Probability
0.39%

33.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= e8f69799810c32dd40c6724d829eccc70baad07f, < bf785a303e5faad16439c563826a07cb811856c8; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 7061aafc680e14e22b191f178b768886475f8524; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 533344a00ad968181e60d0980c076a9d0de57482; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 9e2a2f98e8c0197108c6d97a1fa43bfd89071c30; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 1ae7aee395245874d797890380d9192bd858fb7e; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 7ba87509c54cd519e7ed362e0c85e8431f066a18; >= e8f69799810c32dd40c6724d829eccc70baad07f, < 08e835f5ec6e261c79d8c39f8618b3af29e3b0da; >= e8f69799810c32dd40c6724d829eccc70baad07f, < fc6d80eb504458d6416b75a94188b268c95c6533
LinuxLinux4.18

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-98549?
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.
How severe is CVE-2026-98549?
CVE-2026-98549 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.39% probability of exploitation in the next 30 days.
How do I fix CVE-2026-98549?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST