# CVE-2026-35347: uutils coreutils comm Silent Data Loss or Denial of Service via Improper Input Validation

> The comm utility in uutils coreutils can cause denial of service or silent data loss when processing non-regular file inputs like FIFOs or pipes.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L`)
- **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:** 22 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-35347, GHSA-3wfc-mgpm-9rq6, UBUNTU-CVE-2026-35347

## What is CVE-2026-35347?

CVE-2026-35347 is a medium-severity denial of service vulnerability in Uutils coreutils, published on 22 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The comm utility in uutils coreutils incorrectly consumes data from non-regular file inputs before performing comparison operations. The are_files_identical function opens and reads from both input paths to compare content without first verifying if the paths refer to regular files. If an input path is a FIFO or a pipe, this pre-read operation drains the stream, leading to silent data loss before the actual comparison logic is executed. Additionally, the utility may hang indefinitely if it attempts to pre-read from infinite streams like /dev/zero.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-35347?

2 open source packages ship an affected version, including uu_comm. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `uu_comm` | crates.io | All versions | 0.6.0 |
| `uu_comm` | crates.io | All versions | 0.6.0 |

Products: Uutils Coreutils.

## How do I fix CVE-2026-35347?

Upgrade uu_comm to 0.6.0 or later.

## Is CVE-2026-35347 being exploited?

There is no known exploitation of CVE-2026-35347 in the wild and no public exploit code.

## Other vulnerabilities in Uutils coreutils

- [CVE-2026-35338](https://insights.sbomify.com/CVE-2026-35338/): uutils coreutils chmod Path Traversal Bypass of --preserve-root (high 7.3)
- [CVE-2026-35368](https://insights.sbomify.com/CVE-2026-35368/): uutils coreutils chroot Local Privilege Escalation and chroot Escape in via Name Service Switch (NSS) Injection (high 7.2)
- [CVE-2026-35341](https://insights.sbomify.com/CVE-2026-35341/): uutils coreutils mkfifo Unauthorized Permission Change on Existing Files (high 7.1)
- [CVE-2026-35352](https://insights.sbomify.com/CVE-2026-35352/): uutils coreutils mkfifo Privilege Escalation via TOCTOU Race Condition (high 7.0)
- [CVE-2026-35349](https://insights.sbomify.com/CVE-2026-35349/): uutils coreutils Path-Based Safety Bypass with --preserve-root (medium 6.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35347 and fix it if it is affected.

What it is: CVE-2026-35347 is a medium-severity denial of service vulnerability in Uutils coreutils, published on 22 Apr 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-2026-35347 in the wild and no public exploit code.

Affected packages and fixed versions:
- uu_comm (crates.io): affected all versions; fixed in 0.6.0
- uu_comm (crates.io): affected all versions; fixed in 0.6.0

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-2026-35347/ (Markdown: https://insights.sbomify.com/CVE-2026-35347/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35347
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35347
- OSV: https://osv.dev/vulnerability/CVE-2026-35347

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35347/
Summaries are generated and may contain mistakes; the official description above is the record.