CVE-2026-27830 concerns a critical deserialization vulnerability in the c3p0 JDBC connection pooling library, specifically affecting versions prior to 0.12.0. The vulnerability centers on the userOverridesAsString property of c3p0's ConnectionPoolDataSource implementations, which was stored as a hex-encoded Java-serialized object representing a nested Map structure. This design flaw allows attackers who can reset this property or inject malicious serialized objects or javax.naming.Reference instances to cause the application to deserialize untrusted data. The deserialization process can trigger execution of arbitrary code on the application's classpath. The threat is significantly worsened by vulnerabilities in c3p0's dependency, mchange-commons-java, which includes early JNDI functionality with insufficient restrictions on remote factoryClassLocation values. Attackers can exploit this to embed JNDI references that cause the application to fetch and execute malicious code from remote servers. The vulnerability requires at least low privileges (PR:L) and no user interaction, but the attacker must be able to influence the vulnerable property. The scope and impact are high, affecting confidentiality, integrity, and availability. The fix in c3p0 version 0.12.0 replaces the unsafe serialized object format with a safe CSV-based format and upgrades mchange-commons-java to version 0.4.0+, which restricts remote JNDI lookups and enforces name guarding to prevent injection of malicious JNDI names. No supported workaround exists for versions prior to 0.12.0, making upgrading imperative. This vulnerability is tracked under CWE-502 (Deserialization of Untrusted Data) and CWE-94 (Code Injection).

The impact of CVE-2026-27830 is severe for organizations using vulnerable versions of c3p0, especially in enterprise Java applications relying on JDBC connection pooling. Successful exploitation can lead to remote code execution within the context of the affected application, potentially allowing attackers to execute arbitrary commands, deploy malware, or move laterally within the network. This compromises confidentiality, integrity, and availability of systems and data. Given c3p0's widespread use in Java-based enterprise environments, the vulnerability poses a significant risk to financial institutions, healthcare providers, government agencies, and large enterprises that rely on Java applications for critical operations. The ability to exploit this vulnerability remotely without user interaction and with low privileges increases the attack surface. Additionally, the exploitation could be leveraged to bypass existing security controls, escalate privileges, or establish persistent footholds. The lack of a workaround for older versions further exacerbates the risk, making timely patching essential to prevent potential breaches and operational disruptions.

To mitigate CVE-2026-27830, organizations should immediately upgrade all c3p0 instances to version 0.12.0 or later, which replaces the vulnerable serialized object format with a safe CSV-based format and includes hardened JNDI handling in the updated mchange-commons-java dependency (version 0.4.0+). Review and audit all configurations and code that interact with the userOverridesAsString property to ensure no legacy serialized data or unsafe manipulations remain. Disable or restrict any external access to JNDI interfaces and ensure that network segmentation limits exposure of Java applications to untrusted networks. Implement strict input validation and access controls around any components that can influence connection pool configurations. Monitor application logs and network traffic for unusual JNDI lookups or deserialization attempts. Employ runtime application self-protection (RASP) or Java security managers to detect or block unauthorized deserialization or code loading. If upgrading immediately is not feasible, isolate affected systems and restrict access to minimize exploitation risk, but note that no supported workaround exists for versions prior to 0.12.0. Finally, maintain an inventory of all Java applications using c3p0 to ensure comprehensive remediation.