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Vulnerabilities

Vulnerability · CVE-2026-80793

ipv4: reject undersized MTUs in ip_do_fragment()

Published Sep 4, 2026 · catalog updated Oct 27, 2026 · BSI

Last checked Oct 29, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-80793. EPSS is 0.19%. Act only if a listed version of BSI is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.19%
Remediation
Not established
Affected products
Linux Kernel

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Linux Kernel2.6.12 → 5.10.267; 5.11.0 → 5.15.218; 5.16.0 → 6.1.185

How to fix CVE-2026-80793

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-80793. EPSS is 0.19%. Act only if a listed version of BSI is installed.

Which versions are affected?

Compare what you have installed with Kernel 2.6.12 → 5.10.267; 5.11.0 → 5.15.218; 5.16.0 → 6.1.185. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.19%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 26, 2026 · BSI CERT-Bund

    Detected

    CVE-2026-80793 is listed by Linux Kernel: Mehrere Schwachstellen.

  2. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.267; Kernel fixed in 5.15.218; Kernel fixed in 6.1.185; Kernel fixed in 6.6.154

  3. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.267; 5.11.0

  4. Oct 27, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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 fo

Sources

References

Freshness

Last verified in this catalog Oct 29, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • OpenSSF OSV / OSV ScannerOct 28, 2026
  • CVE.orgOct 27, 2026
  • BSI CERT-BundOct 26, 2026