CVE-2021-21239

Open default xmlsec1 key-type preference

MEDIUM
6.5
CVSS Score
Published: January 21, 2021 at 02:15 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
3 products affected across 3 vendorsDebian LinuxPYSAML2Project PYSAML2

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1%

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. 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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 6.5.0
Affected range stops below 6.5.0, so it looks safe — our inference, not a vendor statement
v < 6.5.0
Affected range stops below 6.5.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-347

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