CVE-2026-27830 Overview
CVE-2026-27830 is a critical insecure deserialization vulnerability affecting c3p0, a widely-used JDBC Connection pooling library for Java applications. The vulnerability allows attackers to execute arbitrary code through maliciously crafted Java-serialized objects and javax.naming.Reference instances. The flaw exists in multiple c3p0 ConnectionPoolDataSource implementations that maintain a property called userOverridesAsString as a hex-encoded serialized object, creating a dangerous attack surface when combined with vulnerabilities in the mchange-commons-java dependency.
Critical Impact
Attackers with adjacent network access can achieve remote code execution by exploiting the insecure deserialization of the userOverridesAsString property, potentially leading to complete system compromise through JNDI injection attacks.
Affected Products
- c3p0 versions prior to 0.12.0
- Applications using vulnerable c3p0 ConnectionPoolDataSource implementations
- Systems with mchange-commons-java versions prior to 0.4.0
Discovery Timeline
- 2026-02-26 - CVE CVE-2026-27830 published to NVD
- 2026-02-26 - Last updated in NVD database
Technical Details for CVE-2026-27830
Vulnerability Analysis
This vulnerability is classified as CWE-94 (Code Injection) and stems from the unsafe handling of serialized Java objects in the c3p0 connection pooling library. The userOverridesAsString property, which conceptually represents a Map<String,Map<String,String>> data structure, was implemented using hex-encoded serialized objects prior to version 0.12.0.
The vulnerability is significantly amplified by flaws in c3p0's primary dependency, mchange-commons-java, which includes code that mirrors early JNDI implementations with ungated support for remote factoryClassLocation values. This combination creates a potent attack chain where deserialization triggers JNDI lookups that can download and execute malicious code from attacker-controlled servers.
Root Cause
The root cause is the use of Java object serialization as the storage format for a writable Java-Bean property. This design decision introduced a serious security fragility, particularly for objects exposed across JNDI interfaces. The lack of input validation on the userOverridesAsString property allowed arbitrary serialized objects to be injected, including those containing embedded javax.naming.Reference objects pointing to remote code locations.
Attack Vector
The attack requires adjacent network access with low privileges. An attacker able to modify the userOverridesAsString property—either on an existing ConnectionPoolDataSource instance or through malicious serialized objects and javax.naming.Reference instances—can inject "indirectly serialized" objects via JNDI references. When the application deserializes these objects and dereferences the embedded javax.naming.Reference objects, it triggers the download and execution of malicious code from a remote factoryClassLocation controlled by the attacker.
import java.lang.reflect.Method;
import com.mchange.v1.lang.BooleanUtils;
import com.mchange.v2.c3p0.C3P0Registry;
+import com.mchange.v2.csv.MalformedCsvException;
//all internal maps should be HashMaps (the implementation presumes HashMaps)
Source: GitHub Commit Change
The patch introduces CSV-based parsing through MalformedCsvException, indicating the transition from dangerous Java serialization to a safe CSV-based format for the userOverridesAsString property.
Detection Methods for CVE-2026-27830
Indicators of Compromise
- Unusual JNDI lookup requests to external or unknown hosts from Java application processes
- Presence of hex-encoded serialized objects in c3p0 configuration files or database entries
- Network connections from application servers to unexpected remote factoryClassLocation URLs
- Java deserialization errors in application logs related to c3p0 ConnectionPoolDataSource classes
Detection Strategies
- Monitor for outbound JNDI/RMI/LDAP connections from application servers to untrusted destinations
- Implement application-level logging to capture modifications to ConnectionPoolDataSource properties
- Deploy Java runtime security agents capable of detecting deserialization attacks
- Use network intrusion detection systems to identify JNDI injection attack patterns
Monitoring Recommendations
- Enable verbose logging for c3p0 configuration changes and JNDI operations
- Implement alerts for unexpected network connections from Java application processes
- Review application logs for serialization-related exceptions or errors
- Monitor for changes to c3p0 configuration parameters, especially userOverridesAsString
How to Mitigate CVE-2026-27830
Immediate Actions Required
- Upgrade c3p0 to version 0.12.0 or later immediately
- Update mchange-commons-java dependency to version 0.4.0 or later
- Audit all c3p0 configuration files and JNDI bindings for suspicious content
- Review and restrict network egress rules for application servers
Patch Information
The vulnerability has been addressed in c3p0 version 0.12.0, which reimplements the userOverridesAsString property using a safe CSV-based format instead of Java object deserialization. Additionally, c3p0-0.12.0+ depends upon mchange-commons-java 0.4.0+, which gates support for remote factoryClassLocation values through configuration parameters that default to restrictive values. The library also enforces the new mchange-commons-java com.mchange.v2.naming.nameGuardClassName to prevent injection of unexpected, potentially remote JNDI names.
For detailed patch information, refer to the GitHub Security Advisory and the MChange Security Configuration documentation.
Workarounds
- There is no supported workaround for versions of c3p0 prior to 0.12.0
- Implement network-level controls to block outbound JNDI/RMI/LDAP connections as a temporary mitigation
- Consider restricting access to c3p0 configuration properties through application-level access controls
- Deploy a Web Application Firewall (WAF) with deserialization attack detection capabilities
# Configuration example for upgraded c3p0 (0.12.0+)
# Verify restrictive JNDI settings in c3p0 configuration
# c3p0.properties or c3p0-config.xml
# Ensure mchange-commons-java security settings are restrictive
# com.mchange.v2.naming.nameGuardClassName should be enforced
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
