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.
CVE-2025-48994
This medium-severity CVE scores 6.9 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 58% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- Lower severity and no public exploit yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.9
- EG Score
- 6.9(medium)
- EPSS
- 9.1%
- KEV
- Not listed
Published
June 2, 2025
Last Modified
April 15, 2026
References (2)
- security-advisories@githubhttps://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600
- security-advisories@githubhttps://github.com/XML-Security/signxml/security/advisories/GHSA-6vx8-pcwv-xhf4
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| signxml | 0.0.1 ... 4.0.3 (77 versions) | 4.0.4 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 50× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
Showing the most recent 100 of 129 total refreshes for this CVE.
- 2026-07-22 14:07 UTCEPSS rescore
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Frequently asked(5)
What is CVE-2025-48994?
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Dependency Blast Radius
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