CedarJava has policy injection vulnerability

Summary

CedarJava is an open source Java implementation of the Cedar policy language, used for fine-grained authorization decisions. Under certain circumstances, improper input handling could allow policy injection.

Impact

Cedar-expression injection via unescaped toCedarExpr()

The toCedarExpr() method on Cedar Value types does not escape special characters (" or \) when converting values to Cedar source code. If an integrator uses toCedarExpr() to build policy text at runtime from user-controlled values, an actor could inject arbitrary Cedar expressions. For example, injecting || true into a permit ... when { ... } clause could make the permit unconditional, or injecting && false into a forbid clause could prevent the forbid from triggering.

This issue requires the integrator to use toCedarExpr() to build policy text at runtime from user-controlled input.

Impacted versions:

< 4.9

Patches

Addressed in CedarJava version 2.3.6, 3.4.1, and 4.9 and above. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

Validate and sanitize all user-supplied input before passing it to toCedarExpr(). Avoid building policy text at runtime from user-controlled values.

References

If you have any questions or comments about this advisory, we ask that you contact us directly via email to cedar-policy-security@lists.cncf.io. Please do not create a public GitHub issue.