Improper Verification of Cryptographic Signature in Python implementation of SAML2



Published: 2021-01-21 | Updated: 2021-02-04
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2021-21239
CWE-ID CWE-347
Exploitation vector Network
Public exploit N/A
Vulnerable software
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Python implementation of SAML2
Universal components / Libraries / Libraries used by multiple products

Vendor Identity Python

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Improper Verification of Cryptographic Signature

EUVDB-ID: #VU50365

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-21239

CWE-ID: CWE-347 - Improper Verification of Cryptographic Signature

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to manipulate data.

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.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Python implementation of SAML2: 6.0.0 - 6.4.1

External links

http://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99
http://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0
http://github.com/IdentityPython/pysaml2/security/advisories/GHSA-5p3x-r448-pc62
http://pypi.org/project/pysaml2
http://www.aleksey.com/pipermail/xmlsec/2013/009717.html


Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.



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