Vulnerability · Published Jun 2, 2025 · Assigned by GitHub_M
CVE-2025-48995SignXML's signature verification with HMAC is vulnerable to a timing 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 15% 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 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | python-signxml | 4.0.5+dfsg-1 | DEBIAN-CVE-2025-48995 |
| Debian:14 | python-signxml | 4.0.5+dfsg-1 | DEBIAN-CVE-2025-48995 |
| PyPI | signxml | 4.0.4 | PYSEC-2026-1922 |
| PyPI | signxml | 4.0.4 | GHSA-gmhf-gg8w-jw42 |
| Ubuntu:25.10 | python-signxml | no fix listed | UBUNTU-CVE-2025-48995 |
| Ubuntu:26.04:LTS | python-signxml | no fix listed | UBUNTU-CVE-2025-48995 |
| Ubuntu:26.10 | python-signxml | no fix listed | UBUNTU-CVE-2025-48995 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| XML-Security | signxml | < 4.0.4 |
Weakness: CWE-208 · Vector: 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