{"id":"PYSEC-2026-1921","summary":"SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack","details":"When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (`signxml.XMLVerifier.verify(require_x509=False, hmac_key=...`), prior versions of SignXML 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.\n\nStarting 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.","aliases":["CVE-2025-48994","GHSA-6vx8-pcwv-xhf4"],"modified":"2026-07-07T17:48:12.634281520Z","published":"2026-07-07T16:02:53.867049Z","references":[{"type":"WEB","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":"WEB","url":"https://github.com/XML-Security/signxml/commit/e3c0c2b82a3329a65d917830657649c98b8c7600"},{"type":"PACKAGE","url":"https://github.com/XML-Security/signxml"},{"type":"PACKAGE","url":"https://pypi.org/project/signxml"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-6vx8-pcwv-xhf4"}],"affected":[{"package":{"name":"signxml","ecosystem":"PyPI","purl":"pkg:pypi/signxml"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.4"}]}],"versions":["0.0.1","0.1.0","0.1.1","0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.1.7","0.1.8","0.1.9","0.2.0","0.2.1","0.2.2","0.2.3","0.2.4","0.2.5","0.2.6","0.2.7","0.2.8","0.2.9","0.3.0","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.5.0","0.6.0","1.0.0","1.0.1","1.0.2","2.0.0","2.1.4","2.10.0","2.10.1","2.2.0","2.2.1","2.2.2","2.2.3","2.2.4","2.2.6","2.3.0","2.4.0","2.5.2","2.6.0","2.7.0","2.7.1","2.7.2","2.7.3","2.8.0","2.8.1","2.8.2","2.9.0","3.0.0","3.0.1","3.0.2","3.1.0","3.1.1","3.2.0","3.2.1","3.2.2","4.0.0","4.0.1","4.0.2","4.0.3"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/signxml/PYSEC-2026-1921.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}