CVE-2018-4939

What is Adobe ColdFusion?

Adobe ColdFusion is a commercial rapid application development platform and server for building and running dynamic, database-driven websites, still used by many enterprises, government agencies, and universities for legacy business applications. ColdFusion has a long history of serious remote code execution vulnerabilities, and because many organizations run older ColdFusion deployments as part of hard-to-replace legacy systems, it remains a recurring target for attackers scanning the internet for exposed instances.

Overview

CVE-2018-4939 is a critical, unauthenticated deserialization of untrusted data vulnerability affecting ColdFusion. An attacker can send a specially crafted request containing malicious serialized data that, when deserialized by the server, results in arbitrary code execution — with no authentication or user interaction required.

Technical Details

The vulnerability is a Java/BlazeDS-style deserialization flaw (CWE-502): certain ColdFusion components deserialize data received over the network without adequately restricting which object types can be instantiated in the process, or validating that the incoming data is legitimate. As with other deserialization vulnerabilities of this era, an attacker can leverage "gadget chains" present on the server's classpath to convert the act of deserializing a crafted object into execution of arbitrary code, all via a single unauthenticated network request.

Discovery

Adobe disclosed and patched this vulnerability through security bulletin APSB18-14, released in May 2018. No specific third-party researcher credit is confidently documented for this individual CVE.

Exploitation Context

ColdFusion deserialization vulnerabilities of this class have a long track record of active exploitation once patches and technical details become public, as attackers reverse-engineer the fix to build working exploits. CISA's KEV catalog listing confirms this specific vulnerability has been observed exploited in the wild, consistent with the broader pattern of internet-facing, unpatched ColdFusion servers being scanned for and compromised for remote code execution, web shell deployment, and further network access.

Remediation

1. Apply Adobe security bulletin APSB18-14 and all subsequent ColdFusion security updates — ColdFusion has had numerous serious vulnerabilities since, so running a fully current, supported version is essential.
2. Restrict network access to ColdFusion administrative and internal-only endpoints; never expose them directly to the internet without additional access controls.
3. Apply Adobe's ColdFusion lockdown guides, which provide hardening configuration specifically designed to reduce the impact of deserialization and related vulnerabilities.
4. Monitor ColdFusion server logs and file systems for unauthorized web shells or unexpected files, a common indicator of prior exploitation of this vulnerability class.
5. Where legacy ColdFusion applications cannot be promptly updated, place them behind a web application firewall configured to block known deserialization exploit patterns as an interim compensating control.