CVE-2026-68118 (GCVE-0-2026-68118)
Vulnerability from cvelistv5
Published
2026-08-10 11:58
Modified
2026-08-23 12:45
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
tcp: challenge ACK for non-exact RST in SYN-RECEIVED
The SYN-RECEIVED request-socket path in tcp_check_req() accepts an
in-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A
non-exact RST therefore removes the request instead of eliciting a
challenge ACK.
RFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in
SYN-RECEIVED: an exact RST resets the connection, while a non-exact
in-window RST must trigger a challenge ACK and be dropped.
Apply that check before the ACK-field validation, following the RFC
sequence-number, RST, then ACK processing order. Factor the per-netns
challenge ACK quota out of tcp_send_challenge_ack() so request sockets
can share it. Use the request socket's send_ack() callback and its own
out-of-window ACK timestamp to send and rate-limit the response.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 282f23c6ee343126156dd41218b22ece96d747e3 Version: 282f23c6ee343126156dd41218b22ece96d747e3 Version: 282f23c6ee343126156dd41218b22ece96d747e3 Version: 282f23c6ee343126156dd41218b22ece96d747e3 Version: 282f23c6ee343126156dd41218b22ece96d747e3 Version: 86791bbfe5ed7b275be040cfeff049a1624af1b7 Version: 61f69dc4e40e41b0018f00fa4aeb23d3239556fb Version: 34fb350281ced2a72707a5c0064f69992d440edb Version: 3.0.58 ≤ Version: 3.2.37 ≤ Version: 3.4.25 ≤ |
||
{
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{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp_input.c",
"net/ipv4/tcp_minisocks.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"net/ipv4/tcp_input.c",
"net/ipv4/tcp_minisocks.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.6"
},
{
"lessThan": "3.6",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
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"versionEndExcluding": "6.6.153",
"versionStartIncluding": "3.6",
"vulnerable": true
},
{
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{
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{
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{
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},
{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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\u0027s send_ack() callback and its own\nout-of-window ACK timestamp to send and rate-limit the response."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
"version": "3.1"
},
"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 \u2192 __inet_lookup_skb on TCP_NEW_SYN_RECV \u2192 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\u2014only 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\u2014only 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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-23T12:45:51.263Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-68118",
"datePublished": "2026-08-10T11:58:38.000Z",
"dateReserved": "2026-07-30T09:28:09.369Z",
"dateUpdated": "2026-08-23T12:45:51.263Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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