xml-security/signxml · Security
SignXML's signature verification with HMAC is vulnerable to a timing attack
- GHSA ID
- GHSA-gmhf-gg8w-jw42
- CVE ID
- CVE-2025-48995
- Severity
- medium
- Published
- Updated
- CVSS v4
- 6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Description
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.
CWEs
- CWE-208 · Observable Timing Discrepancy