CVE-2026-98549

Status: ReceivedUnscored—

Severity—Unscored

Exploitation probability0.13 %higher than 2% of CVEs

Active exploitationNonot in the CISA catalog

Public exploitNot knownno public code found

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.

Read full descriptionShow less

Both users of the fence are affected:

Fix this in two places, for defense in depth:

Technical details traces, logs and code from the original report

- 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.

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.

CVSS

NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.13 %
Percentile among all scored CVEs: 2
Score date: 10/20/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Linux — Linux Kernel^AI

References

Show 4 references

Raw JSON (NVD)

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{
  "id": "CVE-2026-98549",
  "cveTags": [],
  "metrics": {},
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "e8f69799810c32dd40c6724d829eccc70baad07f",
              "lessThan": "1ae7aee395245874d797890380d9192bd858fb7e",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e8f69799810c32dd40c6724d829eccc70baad07f",
              "lessThan": "7ba87509c54cd519e7ed362e0c85e8431f066a18",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e8f69799810c32dd40c6724d829eccc70baad07f",
              "lessThan": "08e835f5ec6e261c79d8c39f8618b3af29e3b0da",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e8f69799810c32dd40c6724d829eccc70baad07f",
              "lessThan": "fc6d80eb504458d6416b75a94188b268c95c6533",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "include/net/tcp.h"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.18"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "4.18",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.55",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver",
              "lessThanOrEqual": "7.2.*"
            },
            {
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "include/net/tcp.h"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-10-18T16:17:06.913",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/08e835f5ec6e261c79d8c39f8618b3af29e3b0da",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/1ae7aee395245874d797890380d9192bd858fb7e",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/7ba87509c54cd519e7ed362e0c85e8431f066a18",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/fc6d80eb504458d6416b75a94188b268c95c6533",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: prevent collapsing skbs across boundary in rtx queue\n\ntcp_write_collapse_fence() sets TCP_SKB_CB(skb)->eor = 1 on\ntcp_write_queue_tail(sk) to prevent skbs queued after a switch to\ndevice encryption from being collapsed into earlier skbs.\n\nThe fence is a no-op if all earlier data has already been transmitted\nwhen the switch happens: sk->sk_write_queue is empty. The not yet\nacknowledged earlier skbs wait in sk->tcp_rtx_queue with eor 0.\n\nOn a subsequent retransmit or SACK shift, tcp_retrans_try_collapse() or\ntcp_shift_skb_data() can then merge an skb queued after the switch into\none queued before it.\n\nBoth users of the fence are affected:\n\n- psp: devices only encrypt skbs with skb->decrypted set. The merged skb\n  keeps decrypted = 0 from the earlier skb, so merged data sent after\n  psp_sock_assoc_set_tx() is retransmitted in cleartext.\n\n- tls device offload: the merged skb straddles the start marker set in\n  tls_set_device_offload(). The software fallback (fill_sg_in() returns\n  -EINVAL) and the mlx5, nfp and funeth drivers cannot handle such an\n  skb and drop it. Every retransmit rebuilds the same skb, so the\n  connection stalls.\n\nFix this in two places, for defense in depth:\n\n1. Fall back to tcp_rtx_queue_tail(sk) in tcp_write_collapse_fence()\n   when tcp_write_queue_tail(sk) is NULL.\n\n2. Check !skb_cmp_decrypted(to, from) in tcp_skb_can_collapse(), as\n   tcp_skb_can_collapse_rx() does on receive. skb_shift(), which both\n   collapse paths call, already has a DEBUG_NET_WARN_ON_ONCE() for this\n   condition."
    }
  ],
  "lastModified": "2026-10-19T10:19:11.063",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}