tcp: clamp route advmss to TCP_MIN_MSS
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.
CVE-2026-80847
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-80847
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "788fbbf7d61f9742298417c207c91b6db159fbbc",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "eaf4af9bd6975c2eff8d48820937c83032d968dc",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "cfb44c6028e6f979720315e0772bbd0d4d33ed61",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "6b8c20bf61924dfc38fefb145c9f7406d73fae53",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "31cf2349361902769dc323e4dbf4b449795ec288",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1",
"versionType": "git"
}
],
"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"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.13",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2.3",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"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"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-80847
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #46639 · Revision 1
- Added to Heist Feed
- Publisher date