CVE-2020-27846: Signature validation bypass due to XML processing error in github.com/crewjam/saml
Summary
CVE-2020-27846: Signature validation bypass due to XML processing error in github.com/crewjam/saml. Affects github.com/crewjam/saml versions < 0.4.3. Fixed in 0.4.3. How to fix ↓
Also tracked for
- grafana · Bitnami
The same CVE-2020-27846 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
The github.com/crewjam/saml package is a Go library that provides functionality for working with SAML (Security Assertion Markup Language) in both Identity Provider (IdP) and Service Provider (SP) roles. It includes features such as serving SSO (Single Sign-On) requests, validating authentication requests, parsing SAML responses, and validating logout responses. The package is widely used in Go applications for implementing SAML-based authentication and authorization.
Vulnerability Detail
The vulnerability (CVE-2020-27846) arises from the behavior of encoding/xml in the github.com/crewjam/saml package. A specially crafted XML document can exploit an XML Digital Signature processing error, leading to the complete bypass of signature validation. As a result, an unsigned document can appear as if it is signed, potentially allowing unauthorized access or tampering with sensitive information. This vulnerability affects versions 0.0.0 to 0.4.2 of the github.com/crewjam/saml package.
How To Fix
Latest published version: v0.5.1 as of 23 Oct 2026
go get github.com/crewjam/saml@v0.5.1Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.4.3
This is the first release that contains the fix.
go get github.com/crewjam/saml@v0.4.3Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no known workaround for this vulnerability. It is essential to upgrade to the fixed version of the github.com/crewjam/saml package to mitigate the risk.
Conclusion
The vulnerability (CVE-2020-27846) in the github.com/crewjam/saml package allows for the bypass of signature validation in SAML documents. It is crucial for developers to upgrade to version 0.4.3 or later of the package to mitigate the risk. No known workarounds exist for this vulnerability. For further support on vulnerability remediation, contact DevNack.com.
See every vulnerability recorded for github.com/crewjam/saml →
FAQ
The vulnerability allows an attacker to bypass signature validation in SAML documents, potentially leading to unauthorized access or tampering with sensitive information.
You can use the Vulert Playground (https://vulert.com/scanner) to check if your application is affected by this vulnerability. It analyzes your Gopkg.lock file and provides real-time alerts for open-source vulnerabilities.
No, only versions 0.0.0 to 0.4.2 of the github.com/crewjam/saml package are affected. Version 0.4.3 and later include a fix for the vulnerability.
No, there is no known workaround. It is crucial to upgrade to the fixed version of the github.com/crewjam/saml package.
You can find more information about this vulnerability in the CVE-2020-27846 entry and the associated GitHub Security Advisory (GHSA-4hq8-gmxx-h6w9).
References
Related vulnerabilities
Recent vulnerabilities recorded for github.com/crewjam/saml.
