UBUNTU-CVE-2026-21452

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Source

https://ubuntu.com/security/CVE-2026-21452

Import Source

https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json

JSON Data

https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-21452

Upstream

CVE-2026-21452

Published

2026-01-02T21:16:00Z

Modified

2026-01-08T06:11:55.419813Z

Severity

7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Ubuntu - medium

Summary

[none]

Details

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.

References

Affected packages

Ubuntu:20.04:LTS / msgpack-java

Package

Name: msgpack-java
Purl: pkg:deb/ubuntu/msgpack-java@0.8.19-1?arch=source&distro=focal

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

0.*

0.8.18-2

0.8.19-1

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "0.8.19-1",
            "binary_name": "libmsgpack-java"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json"

Ubuntu:22.04:LTS / msgpack-java

Package

Name: msgpack-java
Purl: pkg:deb/ubuntu/msgpack-java@0.9.0-2?arch=source&distro=jammy

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

0.*

0.8.22-2

0.9.0-1

0.9.0-2

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "0.9.0-2",
            "binary_name": "libmsgpack-java"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json"

Ubuntu:24.04:LTS / msgpack-java

Package

Name: msgpack-java
Purl: pkg:deb/ubuntu/msgpack-java@0.9.6-1?arch=source&distro=noble

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

0.*

0.9.5-1

0.9.6-1

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "0.9.6-1",
            "binary_name": "libmsgpack-java"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json"

Ubuntu:25.10 / msgpack-java

Package

Name: msgpack-java
Purl: pkg:deb/ubuntu/msgpack-java@0.9.6-1?arch=source&distro=questing

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

0.*

0.9.6-1

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "0.9.6-1",
            "binary_name": "libmsgpack-java"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json"

Ubuntu:25.04 / msgpack-java

Package

Name: msgpack-java
Purl: pkg:deb/ubuntu/msgpack-java@0.9.6-1?arch=source&distro=plucky

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

0.*

0.9.6-1

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "0.9.6-1",
            "binary_name": "libmsgpack-java"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21452.json"