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Comment by timmclean | Hacker News Reader

Agreed. Unfortunately, some implementations missed that:

https://github.com/namshi/jose/commit/127b4415e66d89b1fcfb5a...

https://github.com/davedoesdev/python-jwt/commit/5ddb71b2ed5...

Thanks for spotting this Tim, I appreciate it. I've patched python-jwt and linked to your article. Please let me know if you file a CVE so I can link to it too.

The docs did say:

  returns: ``(header, claims)`` if the token was verified successfully. The token must pass the following tests:
  - Its signature must verify using the public key or its algorithm must be ``none``.

but passing the responsibility for checking header['alg'] to the caller was the wrong way round so thanks again!

Very good catch. You should file CVEs for these, since it's about as hair-on-fire bad as a security bug can be!

News at 5: Library for securing tokens doesn't secure tokens.

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