# CVE-2026-18508: Tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite

> Attackers can overwrite arbitrary files outside the extraction directory by crafting archives with hardlinks when using the --one-top-level option.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A: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:** 3 Aug 2026
- **Updated:** 22 Sep 2026
- **Also known as:** AZL-94599, CLSA-2026-1789128477, CLSA-2026-1789131413, DEBIAN-CVE-2026-18508, ECHO-94ec-2dbe-8b73, GHSA-4f5j-wqjr-hx49, OESA-2026-3911, OESA-2026-3912, OESA-2026-4081, RHSA-2026:50807, UBUNTU-CVE-2026-18508

## What is CVE-2026-18508?

CVE-2026-18508 is a medium-severity path traversal vulnerability in Redhat Enterprise Linux, published on 3 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

A flaw was found in GNU tar. When extracting an archive with the --one-top-level option, hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-18508?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tar` | Red Hat:hummingbird:1 | All versions | 0:1.35-9.2.hum1 |

Products: Gnu Tar, Redhat Enterprise Linux, Redhat Openshift Container Platform.

## How do I fix CVE-2026-18508?

Apply the vendor's patch.

## Is CVE-2026-18508 being exploited?

There is no known exploitation of CVE-2026-18508 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2005-2541](https://insights.sbomify.com/CVE-2005-2541/): Privilege escalation in n/a (critical 10.0)
- [CVE-2019-9923](https://insights.sbomify.com/CVE-2019-9923/): Null dereference in n/a (high 7.5)
- [CVE-2016-6321](https://insights.sbomify.com/CVE-2016-6321/): Path traversal in n/a (high 7.5)
- [CVE-2007-4131](https://insights.sbomify.com/CVE-2007-4131/): Path traversal in n/a (medium 6.8)
- [CVE-2023-39804](https://insights.sbomify.com/CVE-2023-39804/): Denial of service in n/a (medium 6.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18508 and fix it if it is affected.

What it is: CVE-2026-18508 is a medium-severity path traversal vulnerability in Redhat Enterprise Linux, published on 3 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-2026-18508 in the wild and no public exploit code.

Affected product: Redhat Enterprise 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-2026-18508/ (Markdown: https://insights.sbomify.com/CVE-2026-18508/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18508
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18508
- OSV: https://osv.dev/vulnerability/CVE-2026-18508

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18508/
Summaries are generated and may contain mistakes; the official description above is the record.