CVE-2021-21239
PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability.
Does this matter?
Lower severity and a low EPSS score (1.29%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- EPSS
- 1.29% probability · 70th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Affected
- pysaml2 project/pysaml2 · debian/debian linux
- Source
- security-advisories@github.com
EPSS 1.3% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99Patch, Third Party Advisory
- https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0Third Party Advisory
- https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-5p3x-r448-pc62Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/02/msg00038.htmlMailing List, Third Party Advisory
- https://pypi.org/project/pysaml2Product, Third Party Advisory
- https://www.aleksey.com/pipermail/xmlsec/2013/009717.htmlExploit, Mailing List, Third Party Advisory
- https://github.com/IdentityPython/pysaml2/commit/46578df0695269a16f1c94171f1429873f90ed99Patch, Third Party Advisory
- https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0Third Party Advisory
- https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-5p3x-r448-pc62Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/02/msg00038.htmlMailing List, Third Party Advisory
- https://pypi.org/project/pysaml2Product, Third Party Advisory
- https://www.aleksey.com/pipermail/xmlsec/2013/009717.htmlExploit, Mailing List, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.