CVE-2020-25633: RESTEasy Information Disclosure Flaw

CVE-2020-25633 Overview

A flaw was found in the RESTEasy client in all versions of RESTEasy up to 4.5.6.Final. This vulnerability allows client users to obtain the server's potentially sensitive information when the server receives a WebApplicationException from the RESTEasy client call. The vulnerability is classified as CWE-209 (Generation of Error Message Containing Sensitive Information), making it an Information Disclosure vulnerability that impacts data confidentiality.

Critical Impact

Server-side sensitive information may be exposed to client users through improperly handled WebApplicationException error messages, potentially revealing internal system details, configuration information, or other confidential data.

Affected Products

• Red Hat RESTEasy (all versions up to 4.5.6.Final)
• Quarkus (versions using vulnerable RESTEasy)
• Applications built on RESTEasy client framework

Discovery Timeline

• 2020-09-18 - CVE-2020-25633 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-25633

Vulnerability Analysis

This vulnerability exists in the RESTEasy client's exception handling mechanism. When a WebApplicationException is thrown during a RESTEasy client call, the error handling logic may inadvertently include sensitive server-side information in the response that gets transmitted back to the client.

The flaw stems from improper information filtering in error messages. The RESTEasy framework, which is a JAX-RS implementation used for building RESTful web services in Java, fails to properly sanitize exception details before they are returned to the calling client. This allows potentially sensitive server information—such as stack traces, internal paths, configuration details, or other debug information—to leak through exception responses.

The vulnerability can be exploited remotely over the network without requiring authentication or user interaction, making it accessible to any network-adjacent attacker who can trigger the vulnerable code path.

Root Cause

The root cause is CWE-209: Generation of Error Message Containing Sensitive Information. The RESTEasy client does not properly filter or sanitize the content of WebApplicationException objects before exposing error details to client applications. When the server encounters an error condition and throws this exception type, the full exception context—which may contain sensitive internal details—is transmitted to the client without adequate sanitization.

Attack Vector

The attack vector is network-based. An attacker can exploit this vulnerability by:

1. Making RESTEasy client calls that trigger error conditions on the server
2. Capturing the WebApplicationException responses returned to the client
3. Analyzing the error messages for sensitive information such as internal server paths, configuration details, stack traces, or other confidential data

This information disclosure can be leveraged for reconnaissance to plan more sophisticated attacks against the target system.

The vulnerability requires no special privileges or user interaction to exploit—an attacker simply needs network access to interact with the affected RESTEasy client application.

Detection Methods for CVE-2020-25633

Indicators of Compromise

• Unusual patterns of client requests that intentionally trigger error conditions
• Elevated frequency of WebApplicationException occurrences in application logs
• Client applications receiving verbose error responses containing internal server details
• Log entries showing sensitive information being included in exception responses

Detection Strategies

• Monitor RESTEasy client application logs for WebApplicationException occurrences and review the content being returned
• Implement application-level logging to track when detailed error messages are being transmitted to clients
• Use network monitoring tools to inspect HTTP responses for potentially sensitive information in error payloads
• Conduct code reviews to identify locations where WebApplicationException handling may expose sensitive data

Monitoring Recommendations

• Enable detailed logging for RESTEasy client exception handling to track error message content
• Implement alerting on unusual patterns of error responses from RESTEasy-based services
• Regularly audit application logs for inadvertent information disclosure in error messages
• Deploy application performance monitoring (APM) tools to track exception handling behavior

How to Mitigate CVE-2020-25633

Immediate Actions Required

• Upgrade RESTEasy to a patched version beyond 4.5.6.Final
• Review and sanitize custom exception handlers to prevent sensitive information leakage
• Implement application-level filtering of error message content before client transmission
• Configure RESTEasy to use generic error messages in production environments

Patch Information

Red Hat has addressed this vulnerability in RESTEasy versions released after 4.5.6.Final. Organizations should upgrade to the latest stable release of RESTEasy to remediate this vulnerability. For detailed patch information and guidance, refer to the Red Hat Bug Report CVE-2020-25633.

For Quarkus users, ensure you are using a version that includes the patched RESTEasy dependency.

Workarounds

• Implement custom exception mappers that filter sensitive information from WebApplicationException responses
• Configure application servers to suppress detailed error messages in production environments
• Use a reverse proxy or API gateway to filter and sanitize error responses before they reach clients
• Add exception handling wrappers around RESTEasy client calls to intercept and sanitize error details

# Configuration example - Verify RESTEasy version in Maven projects
# Check pom.xml for RESTEasy dependency version
grep -r "resteasy" pom.xml | grep -i version

# Update RESTEasy to patched version in pom.xml
# Ensure version is higher than 4.5.6.Final
# Example Maven dependency update:
# <dependency>
#     <groupId>org.jboss.resteasy</groupId>
#     <artifactId>resteasy-client</artifactId>
#     <version>4.6.0.Final</version>
# </dependency>