CVE-2026-59947 Composer: URL-embedded HTTP-Basic username leaks to verbose logs (GitHub PAT exposure)
Attackers can view GitHub Personal Access Tokens in debug logs when Composer runs with high verbosity, exposing sensitive credentials.
- 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
What is CVE-2026-59947?
CVE-2026-59947 is a medium-severity vulnerability in composer, published on 8 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Composer is a dependency Manager for the PHP language. Prior to 2.2.29 and 2.10.2, when Composer is run with -vvv debug verbosity, it could print a credential embedded in the username slot of a repository or package URL, such as a GitHub Personal Access Token in https://TOKEN@host/, to debug output because AuthHelper, Url::sanitize, and ProcessExecutor did not sanitize username-only URL credentials. This issue is fixed in versions 2.2.29 and 2.10.2.
Weakness: CWE-532
Which versions are affected by CVE-2026-59947?
5 open source packages ship an affected version, including composer/composer and composer.
| Package | Affected | Fixed in |
|---|---|---|
composer/composer Packagist | From 1.0.0 | 2.2.29 |
composer/composer Packagist | From 1.0.0 | 2.2.29 |
composer/composer Packagist | From 2.3.0 | 2.10.2 |
composer/composer Packagist | From 2.3.0 | 2.10.2 |
composer Bitnami | From 1.0.0 | 2.2.29, 2.10.2 |
How do I fix CVE-2026-59947?
Upgrade composer/composer to a fixed version for your release line: 2.2.29 or 2.10.2.
Is CVE-2026-59947 being exploited?
There is no known exploitation of CVE-2026-59947 in the wild and no public exploit code.
Sources
Also known as BIT-composer-2026-59947, CLEANSTART-2026-KK97612, DEBIAN-CVE-2026-59947, GHSA-g6xq-892h-64w3, MINI-h4f9-wh6v-6xjx, MINI-q7fc-848c-jx32 and 1 more.