Authentication bypass via unvalidated wrapped SAML signatures
Published Jan 21, 2021 · Updated Aug 3, 2024
Improper signature verification in IdentityPython PySAML2 before 6.5.0 allows remote attackers to forge accepted SAML assertions. The default CryptoBackendXmlSec1 passes malformed XML to xmlsec1 without schema validation, which checks only the first signature in scope and accepts a signed element wrapped inside malformed content. Exploitation requires an application that verifies attacker-supplied signed SAML documents with the default backend, enabling forged assertion content to be trusted.
Summary
What happened
Improper signature verification in IdentityPython PySAML2 before 6.5.0 allows remote attackers to forge accepted SAML assertions. The default CryptoBackendXmlSec1 passes malformed XML to xmlsec1 without schema validation, which checks only the first signature in scope and accepts a signed element wrapped inside malformed content. Exploitation requires an application that verifies attacker-supplied signed SAML documents with the default backend, enabling forged assertion content to be trusted.
The record
- CVE
- CVE-2021-21238
- Published
- Jan 21, 2021
- Updated
- Aug 3, 2024
- Vendor
- IdentityPython
- Product
- PySAML2
- Classifications
- CWE-347, T1606.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 21, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 6.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream XML signature-wrapping regression fixturesproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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