CVE-2025-48995
SignXML's signature verification with HMAC is vulnerable to a timing attack
EPSS 0.24%
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.
How to fix CVE-2025-48995
To remediate CVE-2025-48995, upgrade the affected package to a fixed version below.
- —upgrade to 4.0.5+dfsg-1 or later
- —upgrade to 4.0.4 or later
Is CVE-2025-48995 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 4.0.5+dfsg-1
- from 0, < 4.0.4
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |