CVE Catalog

CVE-2026-80793

Unknown
Published: Translated: NVD NIST

Summary

In ip_do_fragment(), undersized MTUs were not rejected, causing fragmentation to loop and eventually trigger a softlockup. The issue occurs when the effective MTU is smaller than hlen + 8.

Risk Assessment

An attacker can configure a route with a small MTU or forward a packet to a device with a small MTU, causing a system hang (softlockup).

Recommendation

Apply the patch that rejects mtu < hlen + 8 with -EMSGSIZE in ip_do_fragment().

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS