When Composer is run with -vvv (debug verbosity), it could print a credential that was embedded directly in a repository or package URL, but not as a password, to its debug output. Composer already masked the password portion of such URLs, but the username portion was shown in clear text. Because GitHub and several other services support placing an access token in the username position of a URL (for example https://[token]@github.com/owner/repo), a token used that way could end up written to the verbose log in full.
This is an information disclosure issue. The credential is only ever exposed to whoever can already read Composer's debug output.
You are potentially affected only if all of the following apply:
repositories entry in composer.json, in a package dist/source URL - rather than being supplied through auth.json or the COMPOSER_AUTH environment variable.https://TOKEN@host/…). A normal username:password@host pair where the username is an ordinary account name did not expose the password, that was already masked.If you keep credentials in auth.json or environment variables, or you never run Composer at debug verbosity, you were not exposed.
The most realistic exposure is the documented pattern of embedding a GitHub Personal Access Token in a URL's username position on a machine (often CI) that captures verbose output.
The username is now masked the same way the password already was, so an embedded token no longer appears in verbose output (a short, non-secret prefix may be shown to aid debugging, but never the full value).
Fixed in Composer 2.10.2 and the 2.2.29.
There is no configuration setting that prevents outputting credentials while keeping normal behavior.
If you cannot upgrade right away, you can reduce exposure by:
{
"cwe_ids": [
"CWE-532"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-20T21:55:05Z",
"nvd_published_at": "2026-07-08T20:16:59Z",
"severity": "MODERATE"
}