CVE-2026-102467 in Vert.x
Summary
by MITRE • 10/15/2026
In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the WebSocket implementation does not define a maximum number of bytes allocation when decompressing frames or messages. This can be used to implement DDOS attacks with a zip bomb.
The impacted component is io.vertx:vertx-core.
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Analysis
by VulDB Data Team • 10/15/2026
Eclipse Vert.x, specifically within versions 4.0.0 through 4.5.34 and various releases in the 5.x branch up to 5.2.0, contains a critical vulnerability in its WebSocket implementation related to memory management during frame decompression. The core issue stems from the absence of a defined maximum limit for byte allocation when processing compressed data streams. In modern web applications utilizing WebSockets, it is common practice to compress message payloads using algorithms such as DEFLATE or gzip to reduce bandwidth usage and improve transmission efficiency. However, without strict constraints on how much memory can be allocated during the decompression process, an attacker can exploit this lack of validation by sending a specially crafted compressed payload known as a zip bomb.
A zip bomb is designed to have a very small size when compressed but expands into a massive amount of data upon decompression. For instance, a few kilobytes of maliciously constructed input can expand into gigabytes or even terabytes of uncompressed data. When the vulnerable Vert.x server attempts to process such a payload, it allocates memory proportional to the expanded size rather than limiting allocation based on expected message sizes or system constraints. This behavior leads to rapid and uncontrolled consumption of heap space, causing the Java Virtual Machine (JVM) running the application to exhaust its available memory resources. As the garbage collector struggles to keep up with the massive influx of short-lived objects created during decompression, performance degrades significantly before ultimately resulting in an OutOfMemoryError or a complete crash of the service.
The operational impact of this vulnerability is severe, primarily facilitating Denial-of-Service (DoS) attacks against applications relying on WebSocket connections for real-time communication. Because WebSockets maintain persistent connections, attackers can target specific endpoints to exhaust server resources with minimal effort and bandwidth consumption from their side. This makes the attack highly efficient and difficult to mitigate through traditional network-level rate limiting alone, as the resource exhaustion occurs at the application layer after the connection has been established. The vulnerability affects both client-side implementations that process incoming compressed frames and server-side handlers that decompress messages sent by clients, potentially impacting any service built on these affected Vert.x versions that accepts WebSocket traffic with compression enabled.
From a classification perspective, this flaw aligns with CWE-789: Memory Allocation with Unlimited Input Size, which describes scenarios where software allocates memory based on user input without verifying the size of that input against expected limits. It also relates to CWE-400: Uncontrolled Resource Consumption, as the application fails to restrict the amount of system resources consumed by a single request or connection. In terms of offensive security frameworks, this vulnerability supports techniques found in MITRE ATT&CK T1498: Network Denial of Service, specifically under sub-techniques involving resource exhaustion via volumetric attacks at the application layer. The lack of input validation and size constraints allows adversaries to disrupt service availability effectively without needing elevated privileges or complex exploitation chains beyond sending a single malformed message.
To mitigate this vulnerability, organizations must upgrade Eclipse Vert.x to versions outside the affected ranges, specifically ensuring that version 4.5.35 or later is used for the 4.x branch and appropriate patched releases are applied for the 5.x branches as they become available. If immediate upgrading is not feasible, developers should implement custom decompression handlers that enforce strict limits on the maximum size of uncompressed data allowed per frame or message. This can be achieved by wrapping the standard decompressor with a filter that tracks cumulative byte counts and throws an exception if the limit is exceeded before allocation completes. Additionally, configuring JVM heap sizes appropriately and monitoring memory usage metrics in production environments can help detect such attacks earlier, although proactive patching remains the most effective defense against this class of application-layer denial-of-service vulnerabilities.