# CVE-2026-69153: PostCSS path traversal in sourceMappingURL parsing

Source: https://junglewise.ai/threats/cve-2026-69153-postcss-path-traversal-in-sourcemappingurl-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-03. Updated: 2026-08-03  
License: CC BY 4.0 with a link back

CVE-2026-69153 · Severity: medium · CVSS 4 · Published 2026-08-03

PostCSS is a popular tool used by developers to transform CSS styles. A vulnerability exists where an attacker can provide a specially crafted CSS file that forces the tool to read sensitive files (source maps) from the server's filesystem. This could lead to the exposure of source code or internal file paths, particularly in environments like online CSS editors or automated build services.

Technologies: [postcss (npm)](https://junglewise.ai/threats/technologies/postcss). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-69153 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-69153 being exploited in the wild.

**How severe is CVE-2026-69153?** Medium severity, with a CVSS score of 4, published 3 August 2026.

**Which products and versions are affected?** postcss (npm) SEMVER:introduced=0,fixed=8.5.23.

**Is there a fix for CVE-2026-69153?** Yes. postcss (npm): upgrade to 8.5.23 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-69153 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-69153?** Check whether you run postcss (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- postcss (npm): upgrade to 8.5.23 or later

  ```sh
  npm install postcss@8.5.23
  ```


## Technical details

An incomplete fix for a previous path traversal vulnerability (GHSA-6g55-p6wh-862q) allows arbitrary file reads of .map files. In `lib/previous-map.js`, the `loadFile()` function contains a security guard that rejects absolute paths and directory traversal; however, this guard is only executed if the `from` option is set. If PostCSS is invoked without the `from` option, an attacker-controlled `sourceMappingURL` in a CSS comment can specify an absolute path or use `../` to traverse the filesystem. If the target file ends in `.map` and contains valid JSON, PostCSS will read it and disclose its `sources` and `sourcesContent` in the resulting output. This is fixed in version 8.5.23.

## Affected products

- postcss postcss <= 8.5.22

## Identifiers

- CVE-2026-69153
- GHSA-fxqj-rqcc-2cmp

## Timeline

- 2026-07-24: disclosed
- 2026-08-03: advisory

## References

- [https://api.github.com/users/anir0y](https://api.github.com/users/anir0y)
- [https://github.com/anir0y](https://github.com/anir0y)
- [https://api.github.com/users/anir0y/gists%7B/gist_id%7D](https://api.github.com/users/anir0y/gists%7B/gist_id%7D)
- [https://api.github.com/users/anir0y/repos](https://api.github.com/users/anir0y/repos)
- [https://avatars.githubusercontent.com/u/29829469?v=4](https://avatars.githubusercontent.com/u/29829469?v=4)
- [https://api.github.com/users/anir0y/events%7B/privacy%7D](https://api.github.com/users/anir0y/events%7B/privacy%7D)

## Related threats

- [PostCSS path traversal in source map auto-loading](https://junglewise.ai/threats/cve-2026-73646-postcss-path-traversal-in-source-map-auto-loading)
- [PostCSS arbitrary file read via sourceMappingURL path traversal](https://junglewise.ai/threats/cve-2026-45623-postcss-arbitrary-file-read-via-sourcemappingurl-path-traversal)
- [PostCSS has XSS via Unescaped </style> in its CSS Stringify Output](https://junglewise.ai/threats/cve-2026-41305-postcss-has-xss-via-unescaped-style-in-its-css-stringify-output)
- [PostCSS line return parsing error in CSS tokenization](https://junglewise.ai/threats/cve-2023-44270-postcss-line-return-parsing-error-in-css-tokenization)
- [PostCSS regular expression denial of service in previous-map](https://junglewise.ai/threats/cve-2021-23382-postcss-regular-expression-denial-of-service-in-previous-map)