Executive Intelligence Brief

A vulnerability in the undertow HTTP/1.1 chunked-transfer decoder of Red Hat JBoss Enterprise Application Platform (EAP) 7.4 ELS on RHEL 7 allows an unauthenticated attacker to cause a Denial of Service (DoS) by driving the JVM to an OutOfMemory error. The vulnerability has a CVSS score of 7.5 and is not currently being actively exploited. Affected products include various packages such as eap7-activemq-artemis, eap7-glassfish-jsf, and eap7-jackson-annotations, among others. Immediate patching is recommended to prevent potential DoS attacks.

Threat Overview

The vulnerability, tracked as CVE-2026-15561, affects Red Hat JBoss Enterprise Application Platform (EAP) 7.4 ELS on RHEL 7. This platform is widely used for building enterprise-level applications and provides a robust set of tools for developers. The vulnerability specifically targets the undertow HTTP/1.1 chunked-transfer decoder, a component used for handling HTTP requests.

The vulnerability's impact is significant because it allows an unauthenticated attacker to cause a Denial of Service (DoS) on the affected system. By exploiting this flaw, an attacker can drive the JVM (Java Virtual Machine) to an OutOfMemory error, which results in stopping all deployments on the listener. This effectively renders the application platform unavailable, leading to a DoS condition.

Technical Deep Dive

Vulnerability Classification

The vulnerability is classified under CWE-400: Uncontrolled Resource Consumption. This class of vulnerability occurs when an attacker can cause a system to consume excessive resources, such as memory, CPU, or network bandwidth, leading to a denial-of-service condition.

The CVSS vector details for this vulnerability are not explicitly provided, but the CVSS score is given as 7.5, indicating a high severity level.

Root Cause Analysis

The root cause of this vulnerability is the missing limits on size and count in the undertow HTTP/1.1 chunked-transfer decoder. This allows an attacker to send a specially crafted request that can cause the system to consume excessive memory, leading to an OutOfMemory error.

Attack Vector & Chain

The attack vector for this vulnerability is unauthenticated, meaning that an attacker does not need to have any credentials to exploit the vulnerability. The attack can be carried out remotely, and no user interaction is required.

The attack chain involves the following steps:

  • Initial Access: The attacker sends a specially crafted HTTP request to the vulnerable system.
  • Exploitation: The undertow HTTP/1.1 chunked-transfer decoder processes the request without proper limits, causing excessive memory consumption.
  • Impact: The JVM runs out of memory, stopping all deployments on the listener and causing a DoS condition.

Exploitation Scenario Walkthrough

Scenario: Unauthenticated Denial of Service via Malicious HTTP Request

Reconnaissance: An attacker discovers a vulnerable instance of Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 through a network scan or public repository.

Weaponization: The attacker prepares a specially crafted HTTP request that can exploit the vulnerability in the undertow HTTP/1.1 chunked-transfer decoder.

Delivery & Exploitation: The attacker sends the malicious HTTP request to the vulnerable system. The undertow decoder processes the request without proper limits, causing the JVM to consume excessive memory.

Post-Exploitation: The attacker achieves a DoS condition, stopping all deployments on the listener.

Impact Realization: The system becomes unavailable, and legitimate users are unable to access the applications hosted on the platform.

Exploitation in the Wild

The vulnerability is not currently being actively exploited. However, given its high severity and the potential for causing significant disruption, it is essential for organizations to apply patches immediately.

Impact Analysis

Direct Impact

The direct impact of this vulnerability is a Denial of Service (DoS) condition. An unauthenticated attacker can cause the system to become unavailable, leading to potential loss of business and reputation.

Downstream & Cascading Effects

The downstream effects of this vulnerability can include:

  • Supply chain risk: If the vulnerable platform is used in a supply chain, the DoS condition could have cascading effects on dependent systems and services.
  • Regulatory implications: Depending on the industry and region, there may be regulatory requirements for maintaining system availability.
  • Customer data exposure: Although the vulnerability does not directly lead to data exposure, a prolonged DoS condition could impact the ability to provide services to customers.

Affected Products & Versions

The following products and versions are affected:

  • Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7
  • Various packages such as eap7-activemq-artemis, eap7-glassfish-jsf, eap7-jackson-annotations, among others.

Detection & Threat Hunting

Indicators of Compromise

Indicators of compromise (IoCs) for this vulnerability may include:

  • Unusual patterns of memory consumption by the JVM.
  • Increased number of unauthenticated HTTP requests.
  • System logs indicating OutOfMemory errors.

Detection Rules & Signatures

Detection rules for this vulnerability may involve monitoring:

  • HTTP request logs for unusual patterns.
  • JVM memory consumption metrics.
  • System logs for OutOfMemory errors.

Threat Hunting Queries

Threat hunting queries may include:

  • Searching for unauthenticated HTTP requests with suspicious patterns.
  • Identifying systems with high memory consumption by the JVM.
  • Analyzing system logs for indicators of OutOfMemory errors.

Remediation & Hardening

Immediate Actions (0-24 hours)

Apply the patches provided by Red Hat to fix the vulnerability. Ensure that the following packages are updated:

  • eap7-activemq-artemis
  • eap7-glassfish-jsf
  • eap7-jackson-annotations
  • eap7-jackson-core
  • eap7-jackson-databind
  • eap7-jackson-jaxrs-providers
  • eap7-jackson-modules-base

Short-Term Hardening (1-7 days)

In addition to patching, consider the following hardening measures:

  • Implement network segmentation to limit the spread of the attack.
  • Configure WAF rules to detect and block suspicious HTTP requests.
  • Enhance monitoring of system logs and JVM memory consumption.

Strategic Recommendations

Implement a robust vulnerability management program to ensure timely patching of vulnerabilities. Regularly review and update security controls to prevent similar attacks in the future.

Analyst Assessment

The risk of inaction is high due to the potential for significant disruption caused by this vulnerability. Organizations should prioritize patching and implementing additional security controls to prevent exploitation.

Sources