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PYSEC-2026-1922
SignXML's signature verification with HMAC is vulnerable to a timing attack
Quick fix
PYSEC-2026-1922 — signxml: upgrade to the fixed version with the command below.
pip install --upgrade 'signxml>=4.0.4'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.
Are you affected?
Enter the version of the package you're using.
Affected packages
References
- https://github.com/XML-Security/signxml/security/advisories/GHSA-gmhf-gg8w-jw42[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2025-48995[ADVISORY]
- https://github.com/XML-Security/signxml/commit/1b501faaacf34cf978a52dbc6915ec11e27611cd[WEB]
- https://github.com/XML-Security/signxml[PACKAGE]
- https://pypi.org/project/signxml[PACKAGE]
- https://github.com/advisories/GHSA-gmhf-gg8w-jw42[ADVISORY]