Adobe ColdFusion CVE-2026-27304: Brief Summary of a Critical Input Validation Flaw Leading to Arbitrary Code Execution

Introduction

Adobe's April 2026 Patch Tuesday brought a Priority 1 security update for ColdFusion, and the headliner is CVE-2026-27304, a critical Improper Input Validation flaw that enables arbitrary code execution without any user interaction. Given ColdFusion's documented history as a target for initial access into government and enterprise networks, defenders who manage ColdFusion infrastructure need to address this one immediately.

Adobe ColdFusion is a commercial rapid web application development platform used to build and deploy dynamic websites and web applications. According to W3Techs, it accounts for roughly 0.2% of all websites whose server-side programming language is known. That still translates to thousands of enterprise deployments globally, many of which sit in sensitive environments. Because ColdFusion runs in government and financial-sector infrastructure, any critical vulnerability in it is worth attention.

Technical Information

Root Cause

CVE-2026-27304 is classified under CWE-20 (Improper Input Validation). The flaw is insufficient validation of user-supplied input within the ColdFusion application server. ColdFusion is closed source, so no public source code diff is available, but the patch touches three ColdFusion packages: adminapi, administrator, and CCS. This suggests the fix sits in the product's administrative and core configuration services layer.

CVSS Scoring and Attack Vector

The vulnerability carries a CVSS 3.1 base score of 9.3 with the following vector string:

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Breaking this down:

The Adjacent Network attack vector means the attacker must be on the same network segment as the server or an adjacent one. The flaw is not fully remotely exploitable over the open internet. That does not reduce the severity for organizations whose ColdFusion servers are reachable from internal network segments, VPNs, or shared hosting environments.

Attack Flow

Based on the available technical details, exploitation works like this:

1. An attacker with network adjacency to the target ColdFusion server crafts a malicious request designed to bypass the server's input validation.
2. The attacker sends the request to the ColdFusion server. No authentication or user interaction is required.
3. Because the server does not validate the input sufficiently, the attacker can modify variables and gain unauthorized access.
4. That leads to arbitrary code execution in the context of the current user running the ColdFusion process.
5. Because the scope is "Changed," the impact can extend beyond the ColdFusion application itself, to the underlying operating system or other components.

Companion Vulnerabilities in APSB26-38

CVE-2026-27304 is the highest-scoring vulnerability in security bulletin APSB26-38, but it is not the only one. Applying the cumulative update mitigates several critical attack vectors at once:

Patch Information

Adobe released the official patch for CVE-2026-27304 on April 14, 2026, through security bulletin APSB26-38. Adobe delivers the fix entirely through its cumulative hotfix JAR mechanism.

Patched Versions

Both updates are cumulative, so they bundle every previous fix. Administrators who have fallen behind on patching can jump straight to these versions without installing the interim updates first.

Beyond the input validation fix for CVE-2026-27304, these updates also refresh the underlying servlet container. ColdFusion 2025 Update 7 upgrades its bundled Tomcat to 10.1.53.0, and ColdFusion 2023 Update 19 moves to Tomcat 9.0.116.0.

Installation

Administrators can apply the patch from the Package Manager in the ColdFusion Administrator UI by navigating to Package Manager > Packages > Check for Updates > Update. For an offline manual installation, download the hotfix JAR and run it with ColdFusion's bundled JRE:

# ColdFusion 2025 (Windows example)
<cf_root>\jre\bin\java.exe -jar hotfix-007-331586.jar

# ColdFusion 2023 (Linux example)
<cf_root>/jre/bin/java -jar hotfix-019-330899.jar

You must restart ColdFusion after installation. The build number shown in the Administrator should then match the values in the table above, which is a quick way to confirm the patch has taken effect.

Additional Hardening

Adobe recommends several configuration changes alongside patching:

• Update the ColdFusion JDK or JRE LTS version to the latest update release.
• On JEE installations, set the following JVM flag in the startup file:

-Djdk.serialFilter=!org.mozilla.**;!com.sun.syndication.**;!org.apache.commons.beanutils.**;!org.jgroups.**;!com.sun.rowset.**;!com.mysql.cj.jdbc.interceptors.**;!org.apache.commons.collections.**;

• Use the latest MySQL Java connector.
• Apply the security configuration settings in the ColdFusion Security documentation, and review the Lockdown Guides for ColdFusion 2025 and 2023.

Detection Methods

FortiGuard IPS Signature (Active)

The most immediately actionable detection method comes from Fortinet's FortiGuard Labs, which released an IPS signature the same day the vulnerability was published. The signature is cataloged as ID 60660 under the name "Adobe.ColdFusion.CVE-2026-27304.Improper.Input.Validation" and was introduced in IPS database version 36.201 on April 14, 2026. It is available in both the Regular and Extended IPS databases, and it detects crafted requests to ColdFusion servers that attempt to exploit insufficient validation of user-supplied input.

The default action for this signature profile is set to "pass", so administrators should review their IPS policies and enable active blocking where appropriate.

Vulnerability Scanning

Tenable has cataloged CVE-2026-27304 and tracks it as a Critical-severity issue. As of this writing, though, Tenable's plugin page reports that no dedicated Nessus scanning plugin has been released. That is expected for a newly disclosed vulnerability, and Nessus plugins typically follow within days. Until one appears, security teams using Tenable products should monitor for plugin updates and consider running authenticated version checks against their ColdFusion installations.

Version-Based Detection

Exploit-specific network signatures are not available on every platform, so one of the most reliable detection approaches is to identify the vulnerable ColdFusion instances in your environment:

• Adobe ColdFusion 2025: Update 6 and earlier are vulnerable
• Adobe ColdFusion 2023: Update 18 and earlier are vulnerable

Use asset inventory and configuration management tools to enumerate every ColdFusion deployment and flag any instance running below the patched update levels (Update 7 for 2025, Update 19 for 2023).

Network-Level Monitoring

Because the attack vector is Adjacent Network (AV:A), defenders should pay particular attention to traffic aimed at ColdFusion HTTP/HTTPS endpoints from internal or adjacent network segments. No community Snort or Suricata rules have been published for this CVE yet. The FortiGuard IPS signature, which detects malformed or crafted requests targeting ColdFusion's input validation, is a model for the network-level anomalies to watch for.

What Is Not Yet Available

As of publication day, no specific YARA rules, publicly shared indicators of compromise (file hashes, C2 IPs, domains), or open-source IDS/IPS signatures from community repositories (such as Emerging Threats or Snort community rules) have been identified for this CVE. In APSB26-38, Adobe states that it is "not aware of any exploits in the wild" for the issues the bulletin addresses, so threat intelligence feeds are unlikely to carry specific IoCs at this stage.

Affected Systems and Versions

The following Adobe ColdFusion versions are confirmed vulnerable:

• ColdFusion 2025: Update 6 and all earlier versions
• ColdFusion 2023: Update 18 and all earlier versions

The patched versions are:

• ColdFusion 2025: Update 7 (build 2025,0,07,331586)
• ColdFusion 2023: Update 19 (build 2023,0,19,330899)

Both standalone and JEE deployment configurations are affected. Because the attack vector is Adjacent Network, ColdFusion instances reachable from internal networks, shared hosting environments, or VPN-connected segments are at risk even if they are not directly exposed to the public internet.

Vendor Security History

ColdFusion has a documented history as a target for threat actors seeking initial access to enterprise and government networks. In December 2023, CISA released a joint advisory confirming that threat actors had exploited Adobe ColdFusion CVE-2023-26360, an Improper Access Control vulnerability, to gain initial access to government servers. CISA later added that vulnerability to its Known Exploited Vulnerabilities catalog.

Adobe runs a public bug bounty program on HackerOne for external security researchers, and researcher AnirudhAnand reported CVE-2026-27304 through it. The Zero Day Initiative, which also tracks ColdFusion vulnerabilities, assigned CVE-2026-27304 a deployment priority of 1, its highest urgency tier.

ColdFusion vulnerabilities have been weaponized in real-world attacks before, so Priority 1 ColdFusion patches deserve urgent treatment even when no active exploitation has been confirmed at the time of disclosure.

References

• NVD: CVE-2026-27304
• CVE Record: CVE-2026-27304
• Adobe Security Bulletin APSB26-38
• Adobe ColdFusion 2025 Update 7 Release Notes
• Adobe ColdFusion 2023 Update 19 Release Notes
• Zero Day Initiative: The April 2026 Security Update Review
• FortiGuard IPS Signature 60660
• Tenable: CVE-2026-27304
• Tenable: CVE-2026-27304 Plugins
• MS ISAC Advisory: Multiple Vulnerabilities in Adobe Products
• W3Techs: ColdFusion Usage Statistics
• CISA Advisory: Threat Actors Exploiting CVE-2023-26360
• CISA Report: Threat Actors Exploit Adobe ColdFusion CVE-2023-26360