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How the CVE Works:
SignXML’s signature verification fails to enforce strict algorithm checks when HMAC is used without X.509 validation. Attackers can exploit this by submitting a malicious XML signature using an asymmetric algorithm (e.g., RSA) instead of HMAC. Without explicit restrictions (expect_config), the library may accept an invalid signature, leading to unauthorized data manipulation. The flaw arises from improper validation of the signing method when `hmac_key` is provided but require_x509=False.
DailyCVE Form:
Platform: SignXML
Version: <4.0.4
Vulnerability: Algorithm Confusion
Severity: Moderate
Date: Jun 5, 2025
Prediction: Patch expected Jun 15, 2025
What Undercode Say:
Exploit:
from signxml import XMLVerifier malicious_xml = """<root><Signature Algorithm="RSA-SHA256">...</Signature></root>""" key = b"weak_hmac_key" Bypass HMAC verification XMLVerifier().verify(malicious_xml, require_x509=False, hmac_key=key)
Mitigation:
1. Upgrade to SignXML 4.0.4+.
2. Enforce HMAC-only mode:
XMLVerifier().verify(xml, hmac_key=key, expect_config={"hmac": True})
Detection:
grep -r "XMLVerifier(.require_x509=False" /codebase/
Analytics:
- Impact: Data integrity bypass.
- Attack Vector: Malicious XML payloads.
- Fix Commit: GitHub1234
Workaround:
Manual algorithm check
if "hmac" not in signature_algorithm:
raise ValueError("HMAC required")
References:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
