{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98549", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.356Z", "datePublished": "2026-10-18T15:18:17.361Z", "dateUpdated": "2026-10-24T14:09:22.346Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:22.346Z" }, "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 9.1, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - A TCP ACK carrying attacker-controlled SACK blocks enters tcp_v4_rcv() and follows tcp_rcv_established()->tcp_ack()->tcp_sacktag_write_queue()->tcp_shift_skb_data()->tcp_skb_can_collapse(); withholding ACKs also reaches tcp_retrans_try_collapse() through the retransmission timer over routable IP.\nAC:L - A peer can complete a TLS 1.2 handshake while leaving the last server flight unacknowledged, so tls_set_device_offload()->tcp_write_collapse_fence() sees an empty write queue but a live rtx tail; the peer then deterministically causes collapse using SACKs or an RTO, without a race.\nPR:N - tcp_v4_rcv() processes valid ACK/SACK packets for an established socket without a capability or application-authentication check; an ordinary peer of a public kTLS service therefore needs no victim-host privileges.\nUI:N - Once tls_set_device_offload() or psp_sock_assoc_set_tx() installs transmit state, TCP processes the peer's ACK/SACK pattern and retransmission timer automatically, requiring no victim-user action.\nS:U - The faulty tcp_skb_can_collapse()/skb_shift() merge affects the same host kernel's TCP encryption-offload state and does not cross a VM, IOMMU, or sandbox security boundary.\nC:H - tcp_shift_skb_data() can move post-PSP fragments into a pre-PSP skb that retains decrypted=0; psp_skb_get_assoc_rcu() then returns NULL, bypassing mlx5e_psp_handle_tx_skb() and exposing arbitrary post-key stream contents in cleartext.\nI:N - The merge changes skb offload classification but not payload bytes; the paths either transmit those bytes unchanged or drop the skb, with no memory corruption or accepted attacker-controlled modification.\nA:H - fill_sg_in() returns -EINVAL for a kTLS skb spanning the start marker, and mlx5e_ktls_handle_tx_skb(), nfp_net_tls_tx(), and fun_tls_tx() drop it; every retransmission reuses the same merged skb, so the affected connection cannot progress and is lost." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/tcp.h" ], "versions": [ { "version": "e8f69799810c32dd40c6724d829eccc70baad07f", "lessThan": "9e2a2f98e8c0197108c6d97a1fa43bfd89071c30", "status": "affected", "versionType": "git" }, { "version": "e8f69799810c32dd40c6724d829eccc70baad07f", "lessThan": "1ae7aee395245874d797890380d9192bd858fb7e", "status": "affected", "versionType": "git" }, { "version": "e8f69799810c32dd40c6724d829eccc70baad07f", "lessThan": "7ba87509c54cd519e7ed362e0c85e8431f066a18", "status": "affected", "versionType": "git" }, { "version": "e8f69799810c32dd40c6724d829eccc70baad07f", "lessThan": "08e835f5ec6e261c79d8c39f8618b3af29e3b0da", "status": "affected", "versionType": "git" }, { "version": "e8f69799810c32dd40c6724d829eccc70baad07f", "lessThan": "fc6d80eb504458d6416b75a94188b268c95c6533", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/tcp.h" ], "versions": [ { "version": "4.18", "status": "affected" }, { "version": "0", "lessThan": "4.18", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.112", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.55", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.9", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.12.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.18.55" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.2.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/9e2a2f98e8c0197108c6d97a1fa43bfd89071c30" }, { "url": "https://git.kernel.org/stable/c/1ae7aee395245874d797890380d9192bd858fb7e" }, { "url": "https://git.kernel.org/stable/c/7ba87509c54cd519e7ed362e0c85e8431f066a18" }, { "url": "https://git.kernel.org/stable/c/08e835f5ec6e261c79d8c39f8618b3af29e3b0da" }, { "url": "https://git.kernel.org/stable/c/fc6d80eb504458d6416b75a94188b268c95c6533" } ], "title": "tcp: prevent collapsing skbs across boundary in rtx queue", "x_generator": { "engine": "bippy-1.2.0" } } } }