CVE-2026-80847 (GCVE-0-2026-80847)
Vulnerability from cvelistv5 – Published: 2026-09-04 15:54 – Updated: 2026-10-30 12:31
VLAI
EPSS
VEX
Title
tcp: clamp route advmss to TCP_MIN_MSS
Summary
In the Linux kernel, the following vulnerability has been resolved:
tcp: clamp route advmss to TCP_MIN_MSS
tcp_select_initial_window() assumes that callers never pass an MSS
smaller than 1, but route-derived advmss values can violate that
assumption.
A too-small explicit RTAX_ADVMSS is one way to get there, but it is not
the only one. The same divide-by-zero can also be reached through the
"default advmss" path when RTAX_ADVMSS is left at 0 and the effective
advmss is later driven down by route MTU and min_adv_mss.
Introduce a tcp_dst_advmss() helper that clamps route advmss to
TCP_MIN_MSS before TCP consumes it, and use it in the TCP paths that
derive advmss from dst metrics. This keeps the effective MSS from
dropping to zero before tcp_select_initial_window() rounds the receive
window.
Severity
No CVSS data available.
Assigner
References
7 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1aedef9ca04aad427a077c7c427ffd89768038bc
(git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 788fbbf7d61f9742298417c207c91b6db159fbbc (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < eaf4af9bd6975c2eff8d48820937c83032d968dc (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < cfb44c6028e6f979720315e0772bbd0d4d33ed61 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6b8c20bf61924dfc38fefb145c9f7406d73fae53 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 31cf2349361902769dc323e4dbf4b449795ec288 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1 (git) |
guessed | |
| Linux | Linux |
Affected:
2.6.12
Unaffected: 0 , < 2.6.12 (semver) Unaffected: 6.1.191 , ≤ 6.1.* (semver) Unaffected: 6.6.160 , ≤ 6.6.* (semver) Unaffected: 6.12.111 , ≤ 6.12.* (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.1.13 , ≤ 7.1.* (semver) Unaffected: 7.2.3 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp_ipv4.c",
"net/ipv4/tcp_minisocks.c",
"net/ipv4/tcp_output.c",
"net/ipv6/tcp_ipv6.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
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"versionType": "git"
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{
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"versionType": "git"
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{
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"status": "affected",
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"versionType": "git"
},
{
"lessThan": "870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp_ipv4.c",
"net/ipv4/tcp_minisocks.c",
"net/ipv4/tcp_output.c",
"net/ipv6/tcp_ipv6.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"lessThan": "2.6.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.3",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.191",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.160",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.111",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.51",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.13",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2.3",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.3",
"versionStartIncluding": "2.6.12",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: clamp route advmss to TCP_MIN_MSS\n\ntcp_select_initial_window() assumes that callers never pass an MSS\nsmaller than 1, but route-derived advmss values can violate that\nassumption.\n\nA too-small explicit RTAX_ADVMSS is one way to get there, but it is not\nthe only one. The same divide-by-zero can also be reached through the\n\"default advmss\" path when RTAX_ADVMSS is left at 0 and the effective\nadvmss is later driven down by route MTU and min_adv_mss.\n\nIntroduce a tcp_dst_advmss() helper that clamps route advmss to\nTCP_MIN_MSS before TCP consumes it, and use it in the TCP paths that\nderive advmss from dst metrics. This keeps the effective MSS from\ndropping to zero before tcp_select_initial_window() rounds the receive\nwindow."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:31:12.904Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/1aedef9ca04aad427a077c7c427ffd89768038bc"
},
{
"url": "https://git.kernel.org/stable/c/788fbbf7d61f9742298417c207c91b6db159fbbc"
},
{
"url": "https://git.kernel.org/stable/c/eaf4af9bd6975c2eff8d48820937c83032d968dc"
},
{
"url": "https://git.kernel.org/stable/c/cfb44c6028e6f979720315e0772bbd0d4d33ed61"
},
{
"url": "https://git.kernel.org/stable/c/6b8c20bf61924dfc38fefb145c9f7406d73fae53"
},
{
"url": "https://git.kernel.org/stable/c/31cf2349361902769dc323e4dbf4b449795ec288"
},
{
"url": "https://git.kernel.org/stable/c/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1"
}
],
"title": "tcp: clamp route advmss to TCP_MIN_MSS",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-80847",
"datePublished": "2026-09-04T15:54:57.441Z",
"dateReserved": "2026-08-26T14:34:25.797Z",
"dateUpdated": "2026-10-30T12:31:12.904Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-80847",
"date": "2026-11-01",
"epss": "0.00179",
"percentile": "0.07477"
},
"microsoft_vex": {
"current_release_date": "2026-09-24T02:24:09.000Z",
"cve": "CVE-2026-80847",
"id": "msrc_CVE-2026-80847",
"initial_release_date": "2026-09-07T01:52:27.000Z",
"product_status:known_affected": "3",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "tcp: clamp route advmss to TCP_MIN_MSS",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80847.json",
"version": "4"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp_ipv4.c",
"net/ipv4/tcp_minisocks.c",
"net/ipv4/tcp_output.c",
"net/ipv6/tcp_ipv6.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "1aedef9ca04aad427a077c7c427ffd89768038bc",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "788fbbf7d61f9742298417c207c91b6db159fbbc",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "eaf4af9bd6975c2eff8d48820937c83032d968dc",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "cfb44c6028e6f979720315e0772bbd0d4d33ed61",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "6b8c20bf61924dfc38fefb145c9f7406d73fae53",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "31cf2349361902769dc323e4dbf4b449795ec288",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp_ipv4.c",
"net/ipv4/tcp_minisocks.c",
"net/ipv4/tcp_output.c",
"net/ipv6/tcp_ipv6.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"lessThan": "2.6.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.3",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: clamp route advmss to TCP_MIN_MSS\n\ntcp_select_initial_window() assumes that callers never pass an MSS\nsmaller than 1, but route-derived advmss values can violate that\nassumption.\n\nA too-small explicit RTAX_ADVMSS is one way to get there, but it is not\nthe only one. The same divide-by-zero can also be reached through the\n\"default advmss\" path when RTAX_ADVMSS is left at 0 and the effective\nadvmss is later driven down by route MTU and min_adv_mss.\n\nIntroduce a tcp_dst_advmss() helper that clamps route advmss to\nTCP_MIN_MSS before TCP consumes it, and use it in the TCP paths that\nderive advmss from dst metrics. This keeps the effective MSS from\ndropping to zero before tcp_select_initial_window() rounds the receive\nwindow."
}
],
"id": "CVE-2026-80847",
"lastModified": "2026-10-30T13:20:12.263",
"metrics": {},
"published": "2026-09-04T16:18:13.430",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/1aedef9ca04aad427a077c7c427ffd89768038bc"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/31cf2349361902769dc323e4dbf4b449795ec288"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6b8c20bf61924dfc38fefb145c9f7406d73fae53"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/788fbbf7d61f9742298417c207c91b6db159fbbc"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/cfb44c6028e6f979720315e0772bbd0d4d33ed61"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/eaf4af9bd6975c2eff8d48820937c83032d968dc"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-11-01T07:08:19+00:00",
"cve": "CVE-2026-80847",
"id": "CVE-2026-80847",
"initial_release_date": "2026-09-04T00:00:00+00:00",
"product_status:known_affected": "279",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: tcp: clamp route advmss to TCP_MIN_MSS",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80847.json",
"version": "3"
}
}
}
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