CVE-2021-21238: SAML XML Signature wrapping
First published: Thu Jan 21 2021(Updated: )
### 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 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. ### Patches Users should upgrade to pysaml2 `v6.5.0`. ### Workarounds No workaround provided at this point. ### References No references provided at this point. ### Credits - Victor Schönfelder Garcia (isits AG International School of IT Security) - Juraj Somorovsky (Paderborn University) - Vladislav Mladenov (Ruhr University Bochum) ### For more information If you have any questions or comments about this advisory: * Open an issue in [pysaml2](https://github.com/IdentityPython/pysaml2) * Email us at [the incident-response address](mailto:incident-response@idpy.org)
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/pysaml2 | <6.5.0 | 6.5.0 |
| pysaml2 | <6.5.0 |
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Reference Links
- https://github.com/IdentityPython/pysaml2/commit/1d8fd268f5bf887480a403a7a5ef8f048157cc14
- https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0
- https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-f4g9-h89h-jgv9
- https://pypi.org/project/pysaml2
- https://nvd.nist.gov/vuln/detail/CVE-2021-21238
- https://github.com/pypa/advisory-database/tree/main/vulns/pysaml2/PYSEC-2021-48.yaml
- https://github.com/advisories/GHSA-f4g9-h89h-jgv9 (Advisory)
Frequently Asked Questions
What is the severity of CVE-2021-21238?
CVE-2021-21238 is considered to have a moderate severity level due to the potential for invalid SAML documents to bypass verification processes.
How do I fix CVE-2021-21238?
To fix CVE-2021-21238, upgrade to pysaml2 version 6.5.0 or later.
What does CVE-2021-21238 affect?
CVE-2021-21238 affects all users of pysaml2 who utilize the default CryptoBackendXmlSec1 backend for verifying signed SAML documents.
What is the main issue described in CVE-2021-21238?
The main issue in CVE-2021-21238 is the lack of validation against an XML schema for SAML documents in pysaml2 versions up to 6.4.1.
Can I still use pysaml2 if I'm affected by CVE-2021-21238?
While you can still use pysaml2 if affected by CVE-2021-21238, it is essential to upgrade to the secure version to avoid potential security risks.
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