CVE-2025-21617: Guzzle OAuth Subscriber weak PRNG in nonce generation

Executive brief

Guzzle OAuth Subscriber is a software library used to handle authentication for web requests. A security flaw was found where the library generates predictable security tokens (nonces), which could allow an attacker to intercept and reuse legitimate requests if the connection is not encrypted with TLS. This could lead to unauthorized actions or data exposure depending on the specific application implementation.

Technical details

The vulnerability is classified as a Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (CWE-338) within the Oauth1.php component of the Guzzle OAuth Subscriber library. The nonce generation process lacks sufficient entropy, making the resulting values predictable. An attacker could exploit this to perform replay attacks against servers, particularly in environments where TLS is not enforced. The issue is addressed in version 0.8.1 by implementing a more secure random source.

Affected products

• Guzzle oauth-subscriber < 0.8.1

Timeline

• 2025-01-06: advisory: GitHub Advisory published
• 2025-01-06: patched: Version 0.8.1 released

References

• https://api.github.com/users/psyker156
• https://github.com/psyker156
• https://api.github.com/users/psyker156/gists%7B/gist_id%7D
• https://api.github.com/users/psyker156/repos
• https://avatars.githubusercontent.com/u/242220?v=4
• https://api.github.com/users/psyker156/events%7B/privacy%7D