CVE-2026-80847
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.
Affected versions
Linux kernel versions
2.6.12
and later are affected. Fixed in
6.12.111,
6.18.51,
7.1.13,
7.2.3,
7.3
and their respective stable series.
References
5 totalFrequently asked questions
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What is CVE-2026-80847?
CVE-2026-80847 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 2.6.12 onward and has been patched in 6.12.111, 6.18.51, 7.1.13 and others. CVE-2026-80847 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-80847?
Yes. CVE-2026-80847 has been patched. Fixed versions include 6.12.111, 6.18.51, 7.1.13 and others. If you are running Linux kernel 2.6.12 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-80847 actively exploited?
No. CVE-2026-80847 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.