Pysaml2
CVE-2021-21238
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A04:2025 - Cryptographic Failures
ASVS 5.0
V11 - Cryptography Signature verification
|
| Impact | CVSS score of 6.5 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required. |
| Exploit ScenarioDerived | This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the medium-severity affected system. |
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Alert meAnalysisAI
PySAML2 is a pure python implementation of SAML Version 2 Standard. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in pypi
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified under CWE-347. 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. Affected products include: Pysaml2 Project Pysaml2. Version information: Version 2.
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
Affected Products (CPE)NVD
PySAML2 is a pure python implementation of SAML Version 2 Standard. Rated medium severity (CVSS 6.5), this vulnerability
PySAML2 allows remote attackers to conduct XML external entity (XXE) attacks via a crafted SAML XML request or response.
XML External Entity (XXE) vulnerability in PySAML2 4.4.0 and earlier allows remote attackers to read arbitrary files via
PySAML2 before 5.0.0 does not check that the signature in a SAML document is enveloped and thus signature wrapping is ef
Python package pysaml2 version 4.4.0 and earlier reuses the initialization vector across encryptions in the IDP server,
Exploit-DB