CVE-2018-14667 is an expression language injection vulnerability in Red Hat JBoss RichFaces Framework. CISA added it to the Known Exploited Vulnerabilities catalogue on 28 September 2023, which means attackers have used it in real attacks. Red Hat JBoss RichFaces Framework contains an expression language injection vulnerability via the UserResource resource.
What This Vulnerability Means in a RichFaces Application
An expression language injection flaw means untrusted input can be interpreted as code-like expressions rather than plain data. In a web framework such as RichFaces, that turns ordinary request handling into a potential execution path, which is why this class of issue can move quickly from input handling weakness to application compromise.
The key danger is not the syntax itself, but the trust boundary it crosses. If application code passes attacker-controlled content into expression evaluation, the framework may resolve properties, invoke methods, or otherwise process data in ways the developer never intended. That can expose sensitive objects in memory, alter server-side state, or create a route to deeper exploitation depending on the surrounding application design.
Why Expression Language Injection Is Dangerous
Expression language injection is especially serious in server-side component frameworks because the vulnerable evaluation often happens before the application has a chance to apply normal business logic checks. A flaw in a helper resource, templating path, or rendering component can therefore affect much more than the single page or endpoint that appears exposed.
In practice, the blast radius depends on what the expression engine can reach. If it can access request context, session-scoped objects, beans, or other application internals, the attacker may be able to read data, influence application flow, or pivot into broader server-side compromise. That makes this category materially different from a simple input validation bug.
How Organisations Check Exposure and Confirm Impact
Exposure assessment starts with inventory. Organisations need to know whether any deployed applications still use the affected RichFaces framework and whether the vulnerable UserResource path is reachable in production, staging, or exposed test environments. Asset inventory and internet-facing review are both important, because attackability depends on whether the vulnerable code is actually reachable.
Vendor advisories and the CVE Program record should be used to confirm the exact vulnerability identity, while the NIST National Vulnerability Database and the Vulnerability Management Guide help with prioritisation and verification once the asset is identified. For internet-exposed systems, traffic logs, application logs, and reverse-proxy telemetry can help determine whether the vulnerable endpoint has already been probed or abused.
Remediation, Detection, and Post-Compromise Review
When a patch or framework upgrade cannot be applied immediately, organisations should reduce reachability, restrict access to the vulnerable application path, and add compensating controls around request validation and server-side monitoring. Where the application is business-critical, temporary containment matters more than theoretical completeness.
Detection should focus on unusual expression patterns, unexpected evaluation failures, anomalous requests to the affected resource, and any post-exploitation signs such as new server-side state, suspicious outbound connections, or unexplained application behaviour. If exploitation is suspected, review the application for modified templates, altered configuration, and evidence that the attacker used the flaw to reach credentials, session material, or other sensitive runtime objects.
Risk and Threat Considerations
This kind of flaw matters because expression language injection can become a direct server-side execution primitive in the right application context. Even when the initial issue appears narrow, successful abuse can expose data, alter application behaviour, or create a foothold for follow-on compromise.
Failure mechanism: Untrusted input reaches an expression evaluator, and the application treats attacker-controlled content as executable or inspectable server-side logic.
Impact: Attackers may read sensitive objects, tamper with application state, or extend access into broader compromise depending on what the framework exposes.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5, OWASP ASVS and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-10 — Information Input Validation | Expression injection is prevented by validating and constraining untrusted input before evaluation. |
| AU-2 — Event Logging | Successful probes and exploitation attempts must be observable through application and security logs. | |
| Recommendation — Enforce SI-10 to validate and sanitize inputs before any server-side expression handling. Use AU-2 to log requests and events around the vulnerable resource for investigation and alerting. | ||
| OWASP ASVS | V1 — Encoding and Sanitization | Input encoding and sanitization are central to preventing expression payloads from being interpreted as code. |
| V15 — Secure Coding and Architecture | Secure design must prevent user-controlled data from reaching dangerous evaluation paths in the application architecture. | |
| Recommendation — Apply V1 controls to ensure untrusted data cannot become executable expression content. Use V15 to keep untrusted input out of expression-evaluation paths in the design. | ||
| CIS Controls v8 | CIS-16 — Application Software Security | Application-layer vulnerabilities like expression injection are addressed through secure application security practices and testing. |
| Recommendation — Use CIS-16 to test and harden the application against injection flaws before release. | ||
Practitioner Guidance
Why practitioners should care: For legacy Java web applications, framework-level injection often survives long after the original business feature that introduced it, which makes inventory and decommissioning discipline as important as patching. If RichFaces is still present anywhere in the estate, treat every reachable instance as a candidate exposure until proven otherwise.
Common misunderstanding: Teams sometimes assume a rendering or helper component is “just presentation,” but expression evaluation on the server side is still security-relevant code execution. The safe assumption is that any place user input can influence evaluation deserves the same scrutiny as a direct command path.
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Reviewed and updated by the NHIMG editorial team on October 17, 2026.
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