Unknown

CVE-2026-80793 — ipv4: reject undersized MTUs in ip_do_fragment()

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.

Published Sep 4, 2026 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.2%

ahead of 9% of scored CVEs · Oct 26, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < a716a64a4ba68cd46f2745fba2b1099fe8e0aa59≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 515b6816ba0c12d8415c88e5f41e6ec029e35cfa≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 74ce7389f8f562d39015f59a00ef7ad6acd37803≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < b0ea911453ce7210e8200a07a94d2458bd1e6430≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 36e0741833bd823866f8cb9f112f37cea1a70b60≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < d9d1a676b033acabf8e5645f730486d1f8204a3f≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 3556beb8ca86677af2aca5bfbed6f8e790fccc83≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < c8a74adccaf028223054633b532593101dfcc581 and 2 more ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < c0726f0caf8c6b3208552949e17d23634a2f3129version 2.6.12	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 15, 2026 → Oct 26, 2026 · 11 reading(s) · max 0.20%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 4, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 19, 2026 – Oct 19, 2026
1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

11 on the record

github.com/advisories/GHSA-vc8f-29mh-24xv
GitHub Security Advisories
git.kernel.org/stable/c/515b6816ba0c12d8415c88e5f41e6ec029e35cfa
NIST National Vulnerability Database
git.kernel.org/stable/c/3556beb8ca86677af2aca5bfbed6f8e790fccc83
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-80793
GitHub Security Advisories
git.kernel.org/stable/c/c0726f0caf8c6b3208552949e17d23634a2f3129
NIST National Vulnerability Database
git.kernel.org/stable/c/74ce7389f8f562d39015f59a00ef7ad6acd37803
NIST National Vulnerability Database
git.kernel.org/stable/c/d9d1a676b033acabf8e5645f730486d1f8204a3f
NIST National Vulnerability Database
git.kernel.org/stable/c/a716a64a4ba68cd46f2745fba2b1099fe8e0aa59
NIST National Vulnerability Database
git.kernel.org/stable/c/36e0741833bd823866f8cb9f112f37cea1a70b60
NIST National Vulnerability Database
git.kernel.org/stable/c/c8a74adccaf028223054633b532593101dfcc581
NIST National Vulnerability Database
git.kernel.org/stable/c/b0ea911453ce7210e8200a07a94d2458bd1e6430
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-99092 riscv: patch: fix handling of bpf-jit execmem addresses 1d
Unknown CVE-2026-99093 mm: don't schedule deferred kernel page table freeing while booting 1d
Unknown CVE-2026-99095 drm/vc4: drain the hangcheck timer and works on V3D unbind 1d
Unknown CVE-2026-99096 io_uring/register: don't exempt disabled rings from task restrictions 1d
Unknown CVE-2026-99097 tee: shm: reject zero-sized allocations in tee_dyn_shm_alloc_helper() 1d
Unknown CVE-2026-99098 dm-integrity: fix buffer overflow in inline mode with large tag size 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-80793 is "ipv4: reject undersized MTUs in ip_do_fragment()", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.20% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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