CVE-2025-48995

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

Description

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

Link	Tags
https://github.com/XML-Security/signxml/security/advisories/GHSA-gmhf-gg8w-jw42
https://github.com/XML-Security/signxml/commit/1b501faaacf34cf978a52dbc6915ec11e27611cd

Frequently Asked Questions

What is the severity of CVE-2025-48995?: CVE-2025-48995 has been scored as a medium severity vulnerability.
How to fix CVE-2025-48995?: To fix CVE-2025-48995, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2025-48995 being actively exploited in the wild?: As for now, there are no information to confirm that CVE-2025-48995 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-48995?: CVE-2025-48995 affects XML-Security signxml.

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Description

Category

CWE-208 – Observable Timing Discrepancy

References

Frequently Asked Questions