# CVE-2026-72351: gue: validate REMCSUM private option length

> A missing length validation in the Linux kernel GUE protocol allows malformed packets to cause out-of-bounds reads, potentially leading to a denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72351, DEBIAN-CVE-2026-72351, GHSA-pcv5-gx25-24wj, UBUNTU-CVE-2026-72351

## What is CVE-2026-72351?

CVE-2026-72351 is a critical denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

gue: validate REMCSUM private option length

GUE private flags can indicate that remote checksum offload metadata is
present. The private flags field itself is accounted for by
guehdr_flags_len(), but guehdr_priv_flags_len() currently returns 0 even
when GUE_PFLAG_REMCSUM is set.

This lets a packet with only the private flags field pass
validate_gue_flags(), after which gue_remcsum() and gue_gro_remcsum()
read the missing REMCSUM start/offset fields from the following bytes.

Account for GUE_PLEN_REMCSUM when GUE_PFLAG_REMCSUM is present so that
malformed packets are rejected during option validation.

## Which versions are affected by CVE-2026-72351?


## How do I fix CVE-2026-72351?

Apply the vendor's patch.

## Is CVE-2026-72351 being exploited?

There is no known exploitation of CVE-2026-72351 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72351 and fix it if it is affected.

What it is: CVE-2026-72351 is a critical denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72351 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72351/ (Markdown: https://insights.sbomify.com/CVE-2026-72351/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72351
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72351
- OSV: https://osv.dev/vulnerability/CVE-2026-72351

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72351/
Summaries are generated and may contain mistakes; the official description above is the record.