CVE-2024-3884: 
Java vulnerability analysis and mitigation

CVE-2024-3884 is a denial-of-service vulnerability in Undertow, the Java-based non-blocking web server used in Red Hat JBoss Enterprise Application Platform (EAP) and related products. The flaw exists in the FormEncodedDataDefinition.doParse(StreamSourceChannel) method, which lacks size limits when parsing application/x-www-form-urlencoded form data, causing an OutOfMemoryError when processing oversized payloads. It affects Undertow as shipped with Red Hat JBoss EAP 7.x and 8.x, as well as IBM watsonx Data Intelligence. The vulnerability was reported on April 16, 2024, and publicly disclosed on December 3, 2025. It carries a CVSS v3.1 base score of 7.5 (High) (Red Hat CVE, Red Hat Bugzilla).

The root cause is improper input validation (CWE-20) in Undertow's form data parsing logic. Specifically, the FormEncodedDataDefinition.doParse(StreamSourceChannel) method does not enforce any size limit on incoming application/x-www-form-urlencoded request bodies, allowing an attacker to send an arbitrarily large payload that exhausts the JVM heap memory. The attack vector is network-based, requires no authentication, no user interaction, and low attack complexity — any unauthenticated remote user can trigger the condition by submitting a crafted HTTP POST request with an oversized form body. No public proof-of-concept exploit code has been identified (Red Hat Bugzilla, Red Hat CVE).

Successful exploitation causes the Undertow server process to exhaust available JVM heap memory, resulting in an OutOfMemoryError and a remote denial of service. This renders the affected application server unavailable to legitimate users, impacting service availability with no confidentiality or integrity consequences. Applications deployed on Red Hat JBoss EAP 7.x and 8.x, WildFly, and IBM watsonx Data Intelligence that expose endpoints accepting form-encoded data are at risk (Red Hat Bugzilla, Red Hat CVE).

There is no known public proof-of-concept exploit and no evidence of active in-the-wild exploitation as of the time of disclosure. The EPSS score is approximately 0.0029 (0.29%), indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (Red Hat CVE, Feedly).

1. Reconnaissance: Identify internet-facing or network-accessible Undertow-based servers (e.g., Red Hat JBoss EAP instances) using tools like Shodan, Censys, or network scanning tools such as Nmap, targeting HTTP/HTTPS services on standard ports (8080, 8443, 443).
2. Identify form-accepting endpoints: Browse or probe the target application for endpoints that accept HTTP POST requests with Content-Type: application/x-www-form-urlencoded (e.g., login forms, data submission endpoints).
3. Craft oversized payload: Construct an HTTP POST request with an extremely large application/x-www-form-urlencoded body — for example, a key-value pair where the value is repeated millions of times to create a multi-megabyte or gigabyte payload.
4. Send the malicious request: Transmit the crafted request to the target endpoint using tools such as curl, Python requests, or a custom script. Example: curl -X POST http://target:8080/app/endpoint -H 'Content-Type: application/x-www-form-urlencoded' --data-binary @large_payload.txt
5. Trigger OutOfMemory: The Undertow server attempts to parse the entire payload without size restriction, exhausting JVM heap memory and causing an OutOfMemoryError, resulting in server crash or unresponsiveness (Red Hat Bugzilla).

• Network: Unusually large HTTP POST requests (multi-megabyte or larger bodies) with Content-Type: application/x-www-form-urlencoded directed at application endpoints; repeated large POST requests from the same source IP in a short time window.
• Logs: Java heap space errors (java.lang.OutOfMemoryError: Java heap space) in Undertow or JBoss EAP server logs (server.log); application server crash or restart events correlated with large incoming requests in access logs.
• Process: JVM process consuming abnormally high memory (near or at heap limit) as observed via monitoring tools (e.g., JConsole, Prometheus JVM metrics); sudden application server unresponsiveness or restart events.

Red Hat has released patches across multiple JBoss EAP versions addressing this vulnerability. Patched releases include:

• JBoss EAP 8.1.3 (Undertow 2.3.20.SP4): RHSA-2026:0383 (RHEL 8), RHSA-2026:0384 (RHEL 9), RHSA-2026:0386 (text-only)
• JBoss EAP 8.0: RHSA-2025:22773, RHSA-2025:22775, RHSA-2025:22777, RHSA-2026:3889, RHSA-2026:3891, RHSA-2026:3892
• JBoss EAP 7.4 ELS: RHSA-2026:4915, RHSA-2026:4916, RHSA-2026:4917, RHSA-2026:4924
• JBoss EAP 7.1/7.3 EUS: RHSA-2026:6011, RHSA-2026:6012

As interim workarounds, administrators should implement request body size limits at the WAF or reverse proxy layer (e.g., Nginx client_max_body_size, Apache LimitRequestBody), apply rate limiting on form submission endpoints, and monitor JVM heap usage. Upgrading to a patched Undertow version is the definitive fix (Red Hat Bugzilla, RHSA-2026:0383).

The vulnerability was noted in CISA's weekly vulnerability bulletin for the week of December 1, 2025, indicating it was included in routine government security tracking. Security community aggregators such as RedPacket Security and Vulners published alerts shortly after disclosure. No significant independent researcher commentary or major media coverage has been identified beyond standard vulnerability tracking and vendor advisory channels (Red Hat CVE).