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CVE-2026-80847

UnknownEPSS 0.17%

Last modified

CVE-2026-80847 is a vulnerability of currently unknown severity. 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. EPSS estimates a 0.17% chance of exploitation in the next 30 days.

Description

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.

Metrics

EPSS Probability
0.17%

6.1th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cfb44c6028e6f979720315e0772bbd0d4d33ed61; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 6b8c20bf61924dfc38fefb145c9f7406d73fae53; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 31cf2349361902769dc323e4dbf4b449795ec288; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1
LinuxLinux2.6.12

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is 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.
How severe is CVE-2026-80847?
Severity scoring for CVE-2026-80847 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.
How do I fix CVE-2026-80847?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST