Improper Verification of Cryptographic Signature in PySAML2
Impact
All 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.
Patches
Users should upgrade to pysaml2 v6.5.0.
Workarounds
No workaround provided at this point.
References
This issue has been reported in the past at the xmlsec1 mailing list: https://www.aleksey.com/pipermail/xmlsec/2013/009717.html
Credits
- Brian Wolff
For more information
If you have any questions or comments about this advisory:
- Open an issue in pysaml2
- Email us at the incident-response address
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pysaml2 | < 6.5.0 | 6.5.0 |
References
- https://www.aleksey.com/pipermail/xmlsec/2013/009717.html
- https://pypi.org/project/pysaml2
- https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0
- https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-5p3x-r448-pc62
- https://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99
- https://lists.debian.org/debian-lts-announce/2021/02/msg00038.html
- https://nvd.nist.gov/vuln/detail/CVE-2021-21239
- https://github.com/IdentityPython/pysaml2
- https://github.com/pypa/advisory-database/tree/main/vulns/pysaml2/PYSEC-2021-49.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-347- Platform
- Python (PyPI)
- Package
pysaml2- Disclosed
- 21.01.2021
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-49 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5p3x-r448-pc62 - CC BY 4.0
Vulnerability history: pysaml2
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 03.2017 01.2021
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 2
- Medium 3
Disclosures per year
- 2017: 3
- 2018: 1
- 2019: 0
- 2020: 1
- 2021: 2
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
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