{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-68118", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-30T09:28:09.369Z", "datePublished": "2026-08-10T11:58:38.000Z", "dateUpdated": "2026-08-23T12:45:51.263Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-23T12:45:51.263Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: challenge ACK for non-exact RST in SYN-RECEIVED\n\nThe SYN-RECEIVED request-socket path in tcp_check_req() accepts an\nin-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A\nnon-exact RST therefore removes the request instead of eliciting a\nchallenge ACK.\n\nRFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in\nSYN-RECEIVED: an exact RST resets the connection, while a non-exact\nin-window RST must trigger a challenge ACK and be dropped.\n\nApply that check before the ACK-field validation, following the RFC\nsequence-number, RST, then ACK processing order. Factor the per-netns\nchallenge ACK quota out of tcp_send_challenge_ack() so request sockets\ncan share it. Use the request socket's send_ack() callback and its own\nout-of-window ACK timestamp to send and rate-limit the response." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H", "baseScore": 8.2, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The bug is in tcp_check_req() on the core TCP receive path (ip_rcv/tcp_v4_rcv or tcp_v6_rcv → __inet_lookup_skb on TCP_NEW_SYN_RECV → tcp_check_req); any remote host that can deliver TCP segments to an internet-facing listener reaches it with no local access.\nAC:L - An attacker controls the forged RST (source/dest ports, SEQ sweep across the SYN-RECEIVED window up to tcp_synack_window/65535) and can retry on every handshake; no race, rare config, or victim-only state outside attacker influence is required beyond routine IP spoofing or on-path delivery.\nPR:N - Processing occurs on the pre-authentication TCP handshake path for embryonic request sockets; no credentials, capabilities, or local account are needed—only the ability to send (or spoof) TCP packets to the target listener.\nUI:N - Handshake teardown is triggered automatically when the kernel receives the crafted RST during SYN-RECEIVED; no victim must open files, click links, or perform any other action.\nS:U - Impact is confined to incorrect TCP connection-state handling within the same host kernel; it does not cross VM, container, or IOMMU security boundaries.\nC:N - This is a protocol state-machine logic flaw with no memory corruption, out-of-bounds access, use-after-free, or information disclosure—only embryonic request-socket teardown occurs.\nI:L - A non-exact in-window RST causes unauthorized modification of TCP connection state by dropping the embryonic request socket (embryonic_reset/inet_csk_reqsk_queue_drop) instead of preserving it per RFC 5961/RFC 9293.\nA:H - Repeated spoofed in-window RSTs during SYN-RECEIVED can prevent TCP handshakes from completing on arbitrary listening services (HTTPS, SSH, databases, load balancers), causing sustained denial of service without kernel crash." } ] } ], "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", "net/ipv4/tcp_input.c", "net/ipv4/tcp_minisocks.c" ], "versions": [ { "version": "282f23c6ee343126156dd41218b22ece96d747e3", "lessThan": "8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49", "status": "affected", "versionType": "git" }, { "version": "282f23c6ee343126156dd41218b22ece96d747e3", "lessThan": "0fe4636665d14a258de70b4f3e8248e6d42038f1", "status": "affected", "versionType": "git" }, { "version": "282f23c6ee343126156dd41218b22ece96d747e3", "lessThan": "234f9ffbd9b2c1b24ec67200ea3cff07401bec48", "status": "affected", "versionType": "git" }, { "version": "282f23c6ee343126156dd41218b22ece96d747e3", "lessThan": "22cec809b048495310f206d9abbcdbbfbdce3ae3", "status": "affected", "versionType": "git" }, { "version": "282f23c6ee343126156dd41218b22ece96d747e3", "lessThan": "a28c4fcbf774e23b4779cae468e3497a5ad1f4a1", "status": "affected", "versionType": "git" }, { "version": "86791bbfe5ed7b275be040cfeff049a1624af1b7", "status": "affected", "versionType": "git" }, { "version": "61f69dc4e40e41b0018f00fa4aeb23d3239556fb", "status": "affected", "versionType": "git" }, { "version": "34fb350281ced2a72707a5c0064f69992d440edb", "status": "affected", "versionType": "git" }, { "version": "3.0.58", "lessThan": "3.1", "status": "affected", "versionType": "semver" }, { "version": "3.2.37", "lessThan": "3.3", "status": "affected", "versionType": "semver" }, { "version": "3.4.25", "lessThan": "3.5", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/tcp.h", "net/ipv4/tcp_input.c", "net/ipv4/tcp_minisocks.c" ], "versions": [ { "version": "3.6", "status": "affected" }, { "version": "0", "lessThan": "3.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.153", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.105", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.42", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.6", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "3.6", "versionEndExcluding": "6.6.153" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.12.105" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.18.42" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.1.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.58" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2.37" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.4.25" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49" }, { "url": "https://git.kernel.org/stable/c/0fe4636665d14a258de70b4f3e8248e6d42038f1" }, { "url": "https://git.kernel.org/stable/c/234f9ffbd9b2c1b24ec67200ea3cff07401bec48" }, { "url": "https://git.kernel.org/stable/c/22cec809b048495310f206d9abbcdbbfbdce3ae3" }, { "url": "https://git.kernel.org/stable/c/a28c4fcbf774e23b4779cae468e3497a5ad1f4a1" } ], "title": "tcp: challenge ACK for non-exact RST in SYN-RECEIVED", "x_generator": { "engine": "bippy-1.2.0" } } } }