CVE-2025-48995

MEDIUM6.9

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

Published Jun 2, 2025

Modified 1 years ago

Details

SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 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.

References

WEB

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

WEB

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

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2025-48995

CVSS Analysis

CVSS v4.0

6.9

Exploitability

Attack Vector