CVE-2026-55773 Overview
CVE-2026-55773 is a code injection vulnerability [CWE-94] in CedarJava, the open source Java implementation of the Cedar policy language used for fine-grained authorization decisions. The toCedarExpr() method on Cedar Value types fails to escape special characters (" and \) when converting values to Cedar source code. Integrators that build policy text at runtime from user-controlled values can be tricked into embedding attacker-supplied Cedar expressions. An attacker can inject clauses such as || true into a permit block to bypass authorization or && false into a forbid block to suppress denial. Maintainers fixed the flaw in CedarJava versions 2.3.6, 3.4.1, and 4.9.0.
Critical Impact
Attackers with low-privileged access to input flowing into toCedarExpr() can forge Cedar policy expressions to grant unauthorized access or disable forbid rules, breaking the authorization model.
Affected Products
- CedarJava versions prior to 2.3.6 (2.x branch)
- CedarJava versions prior to 3.4.1 (3.x branch)
- CedarJava versions prior to 4.9.0 (4.x branch)
Discovery Timeline
- 2026-07-13 - CVE-2026-55773 published to NVD
- 2026-07-15 - Last updated in NVD database
Technical Details for CVE-2026-55773
Vulnerability Analysis
Cedar is a policy language that evaluates authorization decisions based on principals, actions, and resources. CedarJava exposes a toCedarExpr() helper on Value types that serializes runtime values into Cedar source code. The method emits strings without escaping the Cedar string delimiter (") or the escape character (\).
Integrators that concatenate the output of toCedarExpr() into policy templates at runtime introduce a classic code injection sink. A user-controlled string value is treated as trusted Cedar syntax once it flows through the unsafe serializer. The vulnerability only manifests when integrators construct policies dynamically from untrusted input, but that pattern is common in multi-tenant systems that generate per-tenant policies.
Root Cause
The root cause is missing output encoding in the toCedarExpr() serializer for Cedar Value types. When a Value containing " or \ is converted, the surrounding string quotes are broken and adjacent Cedar syntax becomes attacker-controlled. This is a textbook improper control of code generation weakness classified under [CWE-94].
Attack Vector
An actor supplies a crafted string value to any application field that later feeds toCedarExpr() for runtime policy construction. Injecting " || true || " inside a permit ... when { ... } clause can make the permit unconditional, granting access regardless of the intended constraints. Conversely, injecting " && false && " into a forbid clause neutralizes the deny rule, allowing actions that should have been blocked. Exploitation requires network reachability to the integrator and any privilege level that can influence the injected value.
No verified public proof-of-concept code is available. See the GitHub Security Advisory GHSA-qmch-v2q9-wg4p for authoritative technical details.
Detection Methods for CVE-2026-55773
Indicators of Compromise
- Cedar policy text at runtime containing unexpected ||, &&, or unbalanced " sequences inside when, unless, permit, or forbid clauses
- Authorization decisions that succeed for principals or actions outside their normal scope, correlated with user-supplied attribute values containing quote or backslash characters
- Application logs showing string values passed to toCedarExpr() that include Cedar keywords such as true, false, principal, or resource
Detection Strategies
- Perform static analysis on Java codebases for calls to toCedarExpr() whose output is concatenated into policy strings evaluated by Cedar
- Instrument the CedarJava integration layer to log the final policy source before evaluation and alert on tokens that were not present in the policy template
- Compare dependency manifests (pom.xml, build.gradle) against fixed versions 2.3.6, 3.4.1, and 4.9.0 to identify vulnerable deployments
Monitoring Recommendations
- Enable verbose Cedar policy evaluation logging and forward events to a centralized data lake for anomaly analysis
- Alert on authorization grants that deviate from historical baselines for a given principal or resource
- Track outbound calls to authorization services from tenants that recently submitted attribute values containing special characters
How to Mitigate CVE-2026-55773
Immediate Actions Required
- Upgrade CedarJava to version 2.3.6, 3.4.1, or 4.9.0 depending on the branch in use
- Audit all integrator code paths that call toCedarExpr() on values derived from untrusted input
- Rotate any authorization decisions cached from vulnerable versions and re-evaluate under patched libraries
Patch Information
The Cedar maintainers released fixes in CedarJava 2.3.6, 3.4.1, and 4.9.0 that correctly escape " and \ characters during Cedar source code generation. Full details are published in the Cedar Java GitHub Security Advisory GHSA-qmch-v2q9-wg4p.
Workarounds
- Avoid using toCedarExpr() to build policy text from user-controlled input; use Cedar's parameterized policy templates and slot substitution instead
- Validate and reject input values containing " or \ characters before they reach any policy construction code path
- Isolate policy generation to trusted service accounts and treat any dynamic policy string as untrusted until validated
# Configuration example: pin CedarJava to a patched release in Maven
mvn versions:use-dep-version -Dincludes=com.cedarpolicy:cedar-java -DdepVersion=4.9.0 -DforceVersion=true
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
