CVE-2026-80847 Affecting linux-6.12 package, versions <6.12.111-1~deb12u1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DEBIAN12-LINUX612-20506248
- published5 Oct 2026
- disclosed4 Sept 2026
Introduced: 4 Sep 2026
CVE-2026-80847 (opens in a new tab)How to fix?
Upgrade Debian:12 linux-6.12 to version 6.12.111-1~deb12u1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream linux-6.12 package and not the linux-6.12 package as distributed by Debian.
See How to fix? for Debian:12 relevant fixed versions and status.
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.
References
- https://security-tracker.debian.org/tracker/CVE-2026-80847
- https://git.kernel.org/stable/c/31cf2349361902769dc323e4dbf4b449795ec288
- https://git.kernel.org/stable/c/6b8c20bf61924dfc38fefb145c9f7406d73fae53
- https://git.kernel.org/stable/c/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1
- https://git.kernel.org/stable/c/cfb44c6028e6f979720315e0772bbd0d4d33ed61
- https://git.kernel.org/stable/c/eaf4af9bd6975c2eff8d48820937c83032d968dc