# CVE-2026-72350: netfilter: xt_u32: reject invalid shift counts

> A malformed netfilter u32 rule with invalid shift counts causes undefined behavior in the Linux kernel, potentially leading to denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72350, DEBIAN-CVE-2026-72350, GHSA-3cfm-hj78-94wf, UBUNTU-CVE-2026-72350

## What is CVE-2026-72350?

CVE-2026-72350 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

netfilter: xt_u32: reject invalid shift counts

u32_match_it() executes rule-supplied shift operands on a 32-bit
value. A malformed u32 rule can provide a shift count of 32 or more,
triggering an undefined shift out-of-bounds during packet evaluation.

Validate XT_U32_LEFTSH and XT_U32_RIGHTSH operands in
u32_mt_checkentry() and reject malformed rules before they reach the
packet path.

## Which versions are affected by CVE-2026-72350?


## How do I fix CVE-2026-72350?

Apply the vendor's patch.

## Is CVE-2026-72350 being exploited?

There is no known exploitation of CVE-2026-72350 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72350 and fix it if it is affected.

What it is: CVE-2026-72350 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72350 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-2026-72350/ (Markdown: https://insights.sbomify.com/CVE-2026-72350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72350
- OSV: https://osv.dev/vulnerability/CVE-2026-72350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72350/
Summaries are generated and may contain mistakes; the official description above is the record.