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CVE-2021-46743
CRITICAL · CVSS 9.1
EPSS exploitation probability: 0%
Published 2022-03-29T07:15:07.017 · Last modified 2026-06-17T04:15:25.123

Summary

In Firebase PHP-JWT before 6.0.0, an algorithm-confusion issue (e.g., RS256 / HS256) exists via the kid (aka Key ID) header, when multiple types of keys are loaded in a key ring. This allows an attacker to forge tokens that validate under the incorrect key. NOTE: this provides a straightforward way to use the PHP-JWT library unsafely, but might not be considered a vulnerability in the library itself.

Affected products

google — firebase_php-jwt

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.