Vulnerability · Published Jun 2, 2025 · Assigned by GitHub_M
CVE-2025-48994SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack
Medium 6.9
In plain English
A medium-severity security flaw in signxml from XML-Security. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 14% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 algorithm confusion attack. Unless the user explicitly limits the expected signature algorithms using the `signxml.XMLVerifier.verify(expect_config=...)` setting, an attacker may supply a signature unexpectedly signed with a key other than the provided HMAC key, using a different (asymmetric key) signature algorithm. Starting with SignXML 4.0.4, specifying `hmac_key` causes the set of accepted signature algorithms to be restricted to HMAC only, if not already restricted by the user.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | python-signxml | 4.0.5+dfsg-1 | DEBIAN-CVE-2025-48994 |
| Debian:14 | python-signxml | 4.0.5+dfsg-1 | DEBIAN-CVE-2025-48994 |
| PyPI | signxml | 4.0.4 | PYSEC-2026-1921 |
| PyPI | signxml | 4.0.4 | GHSA-6vx8-pcwv-xhf4 |
| Ubuntu:25.10 | python-signxml | no fix listed | UBUNTU-CVE-2025-48994 |
| Ubuntu:26.04:LTS | python-signxml | no fix listed | UBUNTU-CVE-2025-48994 |
| Ubuntu:26.10 | python-signxml | no fix listed | UBUNTU-CVE-2025-48994 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| XML-Security | signxml | < 4.0.4 |
Weakness: CWE-303 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N