Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-21452— MessagePack-Java Vulnerable to Remote Denial of Service via Malicious .msgpack Model File Triggering Unbounded EXT Payload Allocation

Quick assessment

Affected
msgpack msgpack-java
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MessagePack for Java是MessagePack开源的一个序列化器软件。 MessagePack for Java 0.9.11之前版本存在安全漏洞，该漏洞源于反序列化时未限制有效载荷长度，可能导致拒绝服务。

CVSS 7.5 · High EPSS 0.60% · P48

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-21452

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
MessagePack-Java Vulnerable to Remote Denial of Service via Malicious .msgpack Model File Triggering Unbounded EXT Payload Allocation
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
MessagePack for Java 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MessagePack for Java是MessagePack开源的一个序列化器软件。 MessagePack for Java 0.9.11之前版本存在安全漏洞，该漏洞源于反序列化时未限制有效载荷长度，可能导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
msgpack msgpack-java < 0.9.11 -

II. Public POCs for CVE-2026-21452

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 12025 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
100+ AI POC generations per month

III. Intelligence Information for CVE-2026-21452

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-21452 (1)

Vendor Advisories for CVE-2026-21452 (1)

Other References for CVE-2026-21452 (1)

IV. Related Vulnerabilities

Same product: msgpack-java
Same vendor: msgpack
Same weakness: CWE-400

V. Comments for CVE-2026-21452

No comments yet

Leave a comment