{"id":"CVE-2021-21239","aliases":["GHSA-5p3x-r448-pc62","PYSEC-2021-49"],"url":"https://o3.security/vulnerability/CVE-2021-21239","summary":"Improper Verification of Cryptographic Signature in PySAML2","details":"### Impact\n\nAll users of pysaml2 that use the default `CryptoBackendXmlSec1` backend and need to verify signed SAML documents are impacted. `pysaml2 <= 6.4.1` does not ensure that a signed SAML document is correctly signed. The default `CryptoBackendXmlSec1` backend is using the `xmlsec1` binary to verify the signature of signed SAML documents, but by default, `xmlsec1` accepts any type of key found within the given document. `xmlsec1` needs to be configured explicitly to only use only _x509 certificates_ for the verification process of the SAML document signature.\n\n### Patches\n\nUsers should upgrade to pysaml2 `v6.5.0`.\n\n### Workarounds\n\nNo workaround provided at this point.\n\n### References\n\nThis issue has been reported in the past at the xmlsec1 mailing list:\nhttps://www.aleksey.com/pipermail/xmlsec/2013/009717.html\n\n### Credits\n\n- Brian Wolff\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [pysaml2](https://github.com/IdentityPython/pysaml2)\n* Email us at [the incident-response address](mailto:incident-response@idpy.org)\n","published":"2021-01-21T15:15:14.423Z","modified":"2026-10-24T10:50:06.769004363Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"pysaml2","fixedVersion":"6.5.0"}],"fix":{"url":"https://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99","label":"IdentityPython/pysaml2@46578df"},"references":[{"type":"ADVISORY","url":"https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0"},{"type":"ADVISORY","url":"https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-5p3x-r448-pc62"},{"type":"ADVISORY","url":"https://lists.debian.org/debian-lts-announce/2021/02/msg00038.html"},{"type":"FIX","url":"https://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99"},{"type":"PACKAGE","url":"https://pypi.org/project/pysaml2"},{"type":"EVIDENCE","url":"https://www.aleksey.com/pipermail/xmlsec/2013/009717.html"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21239"},{"type":"PACKAGE","url":"https://github.com/IdentityPython/pysaml2"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/pysaml2/PYSEC-2021-49.yaml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-24T10:50:06.769004363Z"}}