MessagePack for Java is a serializer implementation for Java. A denial-of-service vulnerability exists in versions prior to 0.9.11 when deserializing .msgpack files containing EXT32 objects with attacker-controlled payload lengths. While MessagePack-Java parses extension headers lazily, it later trusts the declared EXT payload length when materializing the extension data. When ExtensionValue.getData() is invoked, the library attempts to allocate a byte array of the declared length without enforcing any upper bound. A malicious .msgpack file of only a few bytes can therefore trigger unbounded heap allocation, resulting in JVM heap exhaustion, process termination, or service unavailability. This vulnerability is triggered during model loading / deserialization, making it a model format vulnerability suitable for remote exploitation. The vulnerability enables a remote denial-of-service attack against applications that deserialize untrusted .msgpack model files using MessagePack for Java. A specially crafted but syntactically valid .msgpack file containing an EXT32 object with an attacker-controlled, excessively large payload length can trigger unbounded memory allocation during deserialization. When the model file is loaded, the library trusts the declared length metadata and attempts to allocate a byte array of that size, leading to rapid heap exhaustion, excessive garbage collection, or immediate JVM termination with an OutOfMemoryError. The attack requires no malformed bytes, user interaction, or elevated privileges and can be exploited remotely in real-world environments such as model registries, inference services, CI/CD pipelines, and cloud-based model hosting platforms that accept or fetch .msgpack artifacts. Because the malicious file is extremely small yet valid, it can bypass basic validation and scanning mechanisms, resulting in complete service unavailability and potential cascading failures in production systems. Version 0.9.11 fixes the vulnerability.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - MessagePack for Java is a serializer implementation for Java. A denial-of-service vulnerability exists in
    versions prior to 0.9.11 when deserializing .msgpack files containing EXT32 objects with attacker-
    controlled payload lengths. While MessagePack-Java parses extension headers lazily, it later trusts the
    declared EXT payload length when materializing the extension data. When ExtensionValue.getData() is
    invoked, the library attempts to allocate a byte array of the declared length without enforcing any upper
    bound. A malicious .msgpack file of only a few bytes can therefore trigger unbounded heap allocation,
    resulting in JVM heap exhaustion, process termination, or service unavailability. This vulnerability is
    triggered during model loading / deserialization, making it a model format vulnerability suitable for
    remote exploitation. The vulnerability enables a remote denial-of-service attack against applications that
    deserialize untrusted .msgpack model files using MessagePack for Java. A specially crafted but
    syntactically valid .msgpack file containing an EXT32 object with an attacker-controlled, excessively
    large payload length can trigger unbounded memory allocation during deserialization. When the model file
    is loaded, the library trusts the declared length metadata and attempts to allocate a byte array of that
    size, leading to rapid heap exhaustion, excessive garbage collection, or immediate JVM termination with an
    OutOfMemoryError. The attack requires no malformed bytes, user interaction, or elevated privileges and can
    be exploited remotely in real-world environments such as model registries, inference services, CI/CD
    pipelines, and cloud-based model hosting platforms that accept or fetch .msgpack artifacts. Because the
    malicious file is extremely small yet valid, it can bypass basic validation and scanning mechanisms,
    resulting in complete service unavailability and potential cascading failures in production systems.
    Version 0.9.11 fixes the vulnerability. (CVE-2026-21452)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - MessagePack for Java is a serializer implementation for Java. A denial-of-service vulnerability exists in     versions prior to 0.9.11 when deserializing .msgpack files containing EXT32 objects with attacker-     controlled payload lengths. While MessagePack-Java parses extension headers lazily, it later trusts the     declared EXT payload length when materializing the extension data. When ExtensionValue.getData() is     invoked, the library attempts to allocate a byte array of the declared length without enforcing any upper     bound. A malicious .msgpack file of only a few bytes can therefore trigger unbounded heap allocation,     resulting in JVM heap exhaustion, process termination, or service unavailability. This vulnerability is     triggered during model loading / deserialization, making it a model format vulnerability suitable for     remote exploitation. The vulnerability enables a remote denial-of-service attack against applications that     deserialize untrusted .msgpack model files using MessagePack for Java. A specially crafted but     syntactically valid .msgpack file containing an EXT32 object with an attacker-controlled, excessively     large payload length can trigger unbounded memory allocation during deserialization. When the model file     is loaded, the library trusts the declared length metadata and attempts to allocate a byte array of that     size, leading to rapid heap exhaustion, excessive garbage collection, or immediate JVM termination with an     OutOfMemoryError. The attack requires no malformed bytes, user interaction, or elevated privileges and can     be exploited remotely in real-world environments such as model registries, inference services, CI/CD     pipelines, and cloud-based model hosting platforms that accept or fetch .msgpack artifacts. Because the     malicious file is extremely small yet valid, it can bypass basic validation and scanning mechanisms,     resulting in complete service unavailability and potential cascading failures in production systems.
    Version 0.9.11 fixes the vulnerability. (CVE-2026-21452)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
436569	SCA: security update for org.msgpack:msgpack-core (GHSA-cw39-r4h6-8j3x)	Tenable Cloud Security	SCA Checks	Local	high
436569	SCA: security update for org.msgpack:msgpack-core (GHSA-cw39-r4h6-8j3x)	Tenable Self-Hosted Container Security	SCA Checks	Local	high
281625	Linux Distros Unpatched Vulnerability : CVE-2026-21452	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-21452

high

Tenable Plugins

high

high

high