CVE-2026-80793
In the Linux kernel, the following vulnerability has been resolved: ipv4: reject undersized MTUs in ip_do_fragment() ip_do_fragment() subtracts the IPv4 header length from the effective MTU and passes the resulting payload MTU to ip_frag_next(). If the effective MTU is smaller than hlen + 8, ip_frag_next() rounds the fragment payload length down to zero. The fragmentation state then never makes forward progress: state->left, state->ptr and state->offset stay unchanged while ip_do_fragment() keeps allocating and transmitting header-only fragments until the softlockup detector fires. This is reproducible with a route installed using "mtu lock 20", but it is also reproducible without route MTU lock, for example by forwarding a packet to a device whose MTU is 20. Fix it in ip_do_fragment() by rejecting mtu < hlen + 8 with -EMSGSIZE, matching the existing IPv6 fragmentation check.
Affected versions
Linux kernel versions
2.6.12
and later are affected. Fixed in
5.10.267,
5.15.218,
6.1.185,
6.6.154,
6.12.106,
6.18.47,
7.1.11,
7.2.1,
7.3
and their respective stable series.
References
9 totalFrequently asked questions
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What is CVE-2026-80793?
CVE-2026-80793 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 2.6.12 onward and has been patched in 5.10.267, 5.15.218, 6.1.185 and others. CVE-2026-80793 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-2026-80793?
Yes. CVE-2026-80793 has been patched. Fixed versions include 5.10.267, 5.15.218, 6.1.185 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-2026-80793 actively exploited?
No. CVE-2026-80793 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.