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NVD / CVE Program· CNA Linux

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

—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Fixed version: Linux Linux 3556beb8ca86677af2aca5bfbed6f8e790fccc83, 36e0741833bd823866f8cb9f112f37cea1a70b60, 515b6816ba0c12d8415c88e5f41e6ec029e35cfa; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.

Low priority for now. Upgrade to Linux Linux 3556beb8ca86677af2aca5bfbed6f8e790fccc83, 36e0741833bd823866f8cb9f112f37cea1a70b60, 515b6816ba0c12d8415c88e5f41e6ec029e35cfa; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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
Nov 6, 2026
EPSS
0.1% · 9th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.12affected
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before a716a64a4ba68cd46f2745fba2b1099fe8e0aa59affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 515b6816ba0c12d8415c88e5f41e6ec029e35cfaaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 74ce7389f8f562d39015f59a00ef7ad6acd37803affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before b0ea911453ce7210e8200a07a94d2458bd1e6430affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 36e0741833bd823866f8cb9f112f37cea1a70b60affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before d9d1a676b033acabf8e5645f730486d1f8204a3faffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 3556beb8ca86677af2aca5bfbed6f8e790fccc83affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before c8a74adccaf028223054633b532593101dfcc581affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before c0726f0caf8c6b3208552949e17d23634a2f3129affected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.187-16.1.187-1
Debian:12linux-6.12before 6.12.107-1~deb12u16.12.107-1~deb12u1
Debian:13linuxbefore 6.12.107-16.12.107-1
Debian:14linuxbefore 7.1.12-17.1.12-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-80791Sep 4, 2026 · nvmet-auth: zero the AUTH_RECEIVE response buffer
    0Monitor
  • ← EarlierCVE-2026-80792Sep 4, 2026 · ipv6: fix use-after-free in ip6_finish_output2()
    0Monitor
  • Later →CVE-2026-80794Sep 4, 2026 · nfc: nci: fix uninit-value in the RF discover/activated NTF handlers
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux3556beb8ca86677af2aca5bfbed6f8e790fccc83Vendor (CNA)
Linux Linux36e0741833bd823866f8cb9f112f37cea1a70b60Vendor (CNA)
Linux Linux515b6816ba0c12d8415c88e5f41e6ec029e35cfaVendor (CNA)
Linux Linux74ce7389f8f562d39015f59a00ef7ad6acd37803Vendor (CNA)
Linux Linuxa716a64a4ba68cd46f2745fba2b1099fe8e0aa59Vendor (CNA)
Linux Linuxb0ea911453ce7210e8200a07a94d2458bd1e6430Vendor (CNA)
Linux Linuxc0726f0caf8c6b3208552949e17d23634a2f3129Vendor (CNA)
Linux Linuxc8a74adccaf028223054633b532593101dfcc581Vendor (CNA)
Linux Linuxd9d1a676b033acabf8e5645f730486d1f8204a3fVendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.107-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Not on record for this CVE: patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records