Read the docs
TI-2025-31123 Aliases CVE-2025-48995GHSA-gmhf-gg8w-jw42

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

Priority LOW 36CWE-208Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-208.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00239 15th percentileScored 2026-11-07
Fix Fixed signxml (XML-Security): 4.0.4signxml (PyPI): 4.0.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
XML-Securitysignxmlbefore 4.0.44.0.4Patch availableCNA
—signxml (PyPI)before 4.0.44.0.4Patch availableGHSA-gmhf-gg8w-jw42
  • signxml VendorXML-Security Affected before 4.0.4 Fixed in 4.0.4 Patch available CNA
  • signxml (PyPI) Vendor— Affected before 4.0.4 Fixed in 4.0.4 Patch available GHSA-gmhf-gg8w-jw42

Remediation

  • Fix · CNA signxml (XML-Security) Fixed in 4.0.4
  • Fix · GHSA-gmhf-gg8w-jw42 signxml (PyPI) Fixed in 4.0.4 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-48995
  2. 2026-10-03 Alias added: GHSA-gmhf-gg8w-jw42

References

Advisory 1

Other 3

  • TI-2025-31122 SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack CVSS 4.0MEDIUM 6.9

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences