{"id":"CVE-2025-48994","aliases":["GHSA-6vx8-pcwv-xhf4","PYSEC-2026-1921"],"url":"https://o3.security/vulnerability/CVE-2025-48994","summary":"SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack","details":"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.","published":"2025-06-02T16:22:08.966Z","modified":"2026-08-12T03:51:23.179858147Z","cvss":null,"epss":{"score":0.00219,"percentile":0.12563,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"signxml","fixedVersion":"4.0.4"}],"fix":{"url":"https://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600","label":"XML-Security/signxml@e3c0c2b"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/48xxx/CVE-2025-48994.json"},{"type":"ADVISORY","url":"https://github.com/XML-Security/signxml/security/advisories/GHSA-6vx8-pcwv-xhf4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-48994"},{"type":"FIX","url":"https://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600"},{"type":"PACKAGE","url":"https://github.com/XML-Security/signxml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:23.179858147Z"}}