{"id":"CVE-2021-21238","aliases":["GHSA-f4g9-h89h-jgv9","PYSEC-2021-48"],"title":"SAML XML Signature wrapping in PySAML2","summary":"SAML XML Signature wrapping in PySAML2","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N","vendor":"pysaml2","product":"pysaml2","ecosystem":"pip","affected":["pysaml2 < 6.5.0"],"patched":["pysaml2 6.5.0"],"published":"2021-01-21","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:49:13.856780354Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-f4g9-h89h-jgv9","references":[{"url":"https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-f4g9-h89h-jgv9"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21238"},{"url":"https://github.com/IdentityPython/pysaml2/commit/1d8fd268f5bf887480a403a7a5ef8f048157cc14"},{"url":"https://github.com/IdentityPython/pysaml2"},{"url":"https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/pysaml2/PYSEC-2021-48.yaml"},{"url":"https://pypi.org/project/pysaml2"}],"tags":["osv","pip"],"epss":0.01078,"epssPercentile":0.63624,"ingestedAt":"2026-09-12T03:13:01.690Z","slug":"CVE-2021-21238","body":"## Overview\n\n### 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 validate the SAML document against an XML schema. This allows invalid XML documents to trick the verification process, by presenting elements with a valid signature inside elements whose content has been malformed. The verification is offloaded to `xmlsec1` and `xmlsec1` will not validate every signature in the given document, but only the first it finds in the given scope.\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\nNo references provided at this point.\n\n### Credits\n\n- Victor Schönfelder Garcia (isits AG International School of IT Security)\n- Juraj Somorovsky (Paderborn University)\n- Vladislav Mladenov (Ruhr University Bochum)\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\n## Affected packages\n\n- `pysaml2 < 6.5.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `pysaml2 6.5.0`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}