# CVE-2026-66486: Improper Output Encoding in GNU cpio

> Attackers can inject terminal control sequences or forge listing entries via crafted cpio archives, affecting users viewing archive contents.

- **Severity:** Medium 4.6 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 10 Aug 2026
- **Updated:** 10 Aug 2026
- **Also known as:** AZL-94689, DEBIAN-CVE-2026-66486, GHSA-p5w5-qcg3-g8gx, OESA-2026-3540, UBUNTU-CVE-2026-66486

## What is CVE-2026-66486?

CVE-2026-66486 is a medium-severity vulnerability in GNU cpio, published on 10 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

GNU cpio is vulnerable to improper encoding or escaping of output in its archive member listing functionality. When listing archive members via cpio -it, member names are printed directly to output without quoting or escaping. An attacker can craft a cpio archive containing member names with embedded newline characters or ANSI escape sequences, causing forged listing entries or terminal control sequence injection when the listing is displayed.

This issue has been fixed in commit 2ff9600c9ef32e88759843cdbde74c8db5ae9b30

Weakness: CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-66486?


## How do I fix CVE-2026-66486?

Apply the vendor's patch.

## Is CVE-2026-66486 being exploited?

There is no known exploitation of CVE-2026-66486 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66486 and fix it if it is affected.

What it is: CVE-2026-66486 is a medium-severity vulnerability in GNU cpio, published on 10 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-66486 in the wild and no public exploit code.

Affected product: GNU cpio. 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-2026-66486/ (Markdown: https://insights.sbomify.com/CVE-2026-66486/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66486
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66486
- OSV: https://osv.dev/vulnerability/CVE-2026-66486

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66486/
Summaries are generated and may contain mistakes; the official description above is the record.