# CVE-2021-21239: Improper Verification of Cryptographic Signature in PySAML2

Source: https://junglewise.ai/threats/cve-2021-21239-improper-verification-of-cryptographic-signature-in-pysaml2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-01-21  
License: CC BY 4.0 with a link back

CVE-2021-21239 · Severity: low · CVSS 3.1 · Published 2021-01-21

PySAML2 is a pure python implementation of SAML Version 2 Standard. PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability. Users of pysaml2 that use the default CryptoBackendXmlSec1 backend and need to verify signed SAML documents are impacted. PySAML2 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. This is fixed in PySAML2 6.5.0.

Technologies: [pysaml2 (PyPI)](https://junglewise.ai/threats/technologies/pypi-pysaml2). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-21239 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-21239 being exploited in the wild.

**How severe is CVE-2021-21239?** Low severity, with a CVSS score of 3.1, published 21 January 2021.

**Which products and versions are affected?** pysaml2 (PyPI) ECOSYSTEM:introduced=0,fixed=6.5.0, GIT:introduced=0,fixed=46578df0695269a16f1c94171f1429873f90ed99|ECOSYSTEM:introduced=0,fixed=6.5.0.

**Is there a fix for CVE-2021-21239?** Yes. pysaml2 (PyPI): upgrade to 6.5.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-21239?** Check whether you run pysaml2 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pysaml2 (PyPI): upgrade to 6.5.0 or later

  ```sh
  pip install "pysaml2>=6.5.0"
  ```


## Affected products

- pysaml2 (PyPI) ECOSYSTEM:introduced=0,fixed=6.5.0, GIT:introduced=0,fixed=46578df0695269a16f1c94171f1429873f90ed99|ECOSYSTEM:introduced=0,fixed=6.5.0

## Identifiers

- CVE-2021-21239
- GHSA-5p3x-r448-pc62
- PYSEC-2021-49

## Related threats

- [SAML XML Signature wrapping in PySAML2](https://junglewise.ai/threats/cve-2021-21238-saml-xml-signature-wrapping-in-pysaml2)
- [Improper Verification of Cryptographic Signature in PySAML2](https://junglewise.ai/threats/cve-2020-5390-improper-verification-of-cryptographic-signature-in-pysaml2)
- [pysaml2 Improper Authentication vulnerability](https://junglewise.ai/threats/cve-2017-1000433-pysaml2-improper-authentication-vulnerability)
- [Pysaml2 improperly initializes encryption vector](https://junglewise.ai/threats/cve-2017-1000246-pysaml2-improperly-initializes-encryption-vector)
- [Pysaml2 does not sanitize XML responses](https://junglewise.ai/threats/cve-2016-10149-pysaml2-does-not-sanitize-xml-responses)