GHSA-gmhf-gg8w-jw42

MEDIUM6.9

SignXML's signature verification with HMAC is vulnerable to a timing attack

Published Jun 5, 2025

Modified 1 years ago

Fix available

Details

When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), prior versions of SignXML are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.

Affected Packages

signxml

PyPI

Fixed in:

4.0.4

References

PACKAGE

https://github.com/XML-Security/signxml

WEB

https://github.com/XML-Security/signxml/commit/1b501faaacf34cf978a52dbc6915ec11e27611cd

WEB

https://github.com/XML-Security/signxml/security/advisories/GHSA-gmhf-gg8w-jw42