# CVE-2026-18477: Tar: tar: toctou in incremental dumpdir 'x' rename handling allows restore path escape

> A local attacker can exploit a race condition in GNU tar's restore process to modify files outside the target directory, potentially leading to privilege escalation.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **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-94602, CLSA-2026-1787335320, CLSA-2026-1787337920, DEBIAN-CVE-2026-18477, ECHO-b8d2-238f-d46b, GHSA-v7fx-gjvh-347c, JLSEC-2026-1344, MINI-f95f-ccg5-864x, OESA-2026-3597, OESA-2026-3598, OESA-2026-3599, OESA-2026-3600, OESA-2026-3870, RHSA-2026:49361, UBUNTU-CVE-2026-18477

## What is CVE-2026-18477?

CVE-2026-18477 is a medium-severity 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 TOCTOU (Time-of-Check Time-of-Use) vulnerability in GNU tar's incremental dumpdir 'X' rename handling allows a local attacker with write access to a directory being backed up to influence the restore process if the attacker has access to the system where the restore is being performed. During restoration, files or directories may be created, renamed or overwritten outside the intended extraction directory. This could lead to unauthorized file modification or, in some cases, privilege escalation. Exploitation does not require the attacker to modify or craft the archive, and standard backup and restore workflows—including extracting into a newly created directory without using the -P option do not mitigate the issue.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-18477?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tar` | Red Hat:hummingbird:1 | All versions | 0:1.35-9.1.hum1 |

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

## How do I fix CVE-2026-18477?

Apply the vendor's patch.

## Is CVE-2026-18477 being exploited?

There is no known exploitation of CVE-2026-18477 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-2026-18477 and fix it if it is affected.

What it is: CVE-2026-18477 is a medium-severity 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-2026-18477 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-2026-18477/ (Markdown: https://insights.sbomify.com/CVE-2026-18477/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18477
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18477
- OSV: https://osv.dev/vulnerability/CVE-2026-18477

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18477/
Summaries are generated and may contain mistakes; the official description above is the record.