CVE-2026-80847
Low risk· EPSS 6%Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel, the TCP stack has an issue where route-derived advmss values can be smaller than 1, leading to a divide-by-zero in tcp_select_initial_window(). The fix introduces a tcp_dst_advmss() helper that clamps advmss to TCP_MIN_MSS.
Risk Assessment
The organization may experience system crashes (panic) or malfunction of TCP connections, potentially affecting network stability.
Recommendation
Apply a Linux kernel update containing the fix that clamps advmss to TCP_MIN_MSS in TCP paths.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

