CVE-2026-93494 in Netty
Summary
by MITRE • 09/18/2026
A flaw was found in Netty's StompSubframeDecoder component. A remote attacker can exploit this vulnerability by sending a specially crafted STOMP frame body without its terminating null byte. This causes the decoder to allocate a ByteBuf (a buffer for bytes) that is never released, leading to a permanent memory leak. Over time, this uncontrolled memory consumption can result in a Denial of Service (DoS) for the application using the affected STOMP codec.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within Netty's StompSubframeDecoder component represents a significant resource management flaw that directly impacts the stability and availability of applications relying on this library for Simple Text Oriented Messaging Protocol communications. The core technical issue stems from an improper handling of frame termination sequences, specifically regarding STOMP frames where the expected terminating null byte is absent or malformed in the incoming data stream. In normal operation, the decoder expects a specific protocol structure to properly delineate message boundaries and manage internal buffer states. When this structural integrity is compromised by a remote attacker sending crafted payloads lacking the required terminator, the underlying ByteBuf allocation mechanism fails to trigger its standard cleanup routines. This results in memory blocks being allocated for processing the malformed input but never subsequently released back to the system's available pool.
This behavior constitutes an uncontrolled resource consumption vulnerability that aligns with CWE-401, which describes missing release of a managed resource after it is used. The consequence of this flaw is a gradual and persistent increase in memory usage within the application process hosting the Netty server or client component. As more maliciously crafted frames are processed over time, the heap space consumed by these unreleased ByteBuf instances expands continuously. This phenomenon effectively creates a slow-burn Denial of Service condition rather than an immediate crash. The affected system remains operational but becomes increasingly sluggish and unresponsive as it struggles to manage the growing memory footprint, eventually leading to OutOfMemoryError exceptions or complete application failure when system limits are exceeded.
From a threat modeling perspective, this vulnerability is exploitable by remote attackers who have network access to the STOMP service endpoint. The attack vector falls under ATT&CK technique T1498, specifically Network Denial of Service via resource exhaustion. Unlike vulnerabilities that allow for arbitrary code execution or data exfiltration, this flaw targets availability rather than confidentiality or integrity. However, its impact on operational continuity is severe, particularly in high-throughput messaging environments where STOMP is commonly used for real-time data exchange between microservices or client applications. The lack of immediate feedback mechanisms means the degradation may go unnoticed until critical performance thresholds are breached, making detection and response challenging without robust memory monitoring tools.
Mitigation strategies must focus on both defensive coding practices within Netty itself and operational safeguards in deployment environments. For developers utilizing affected versions of Netty, upgrading to a patched version that correctly handles malformed STOMP frames is the primary remediation path. The fix typically involves enhancing input validation logic to ensure strict adherence to protocol specifications before allocating substantial buffer resources. Additionally, implementing circuit breakers or rate limiting at the network perimeter can help mitigate the impact by restricting the volume of incoming messages from untrusted sources. Application-level monitoring should also be enhanced to track heap memory usage trends in real-time, allowing for automated scaling or restart procedures when anomalous growth patterns indicative of this leak are detected. By combining software updates with proactive operational controls, organizations can effectively neutralize the risk posed by this resource exhaustion vulnerability and maintain service availability.