CVE-2020-5234

What it is

MessagePack for C# and Unity before version 1.9.11 and 2.1.90 has a vulnerability where untrusted data can lead to DoS attack due to hash collisions and stack overflow. Review the linked GitHub Security Advisory for more information and remediation steps.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account, but needs a user to act. High risk of service disruption.

Exploit odds

1.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-01-31 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:21 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.6% in the next 30 days (EPSS).
• Severity: 4.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-01-31 18:15 UTC

Last modified

2026-06-17 03:21 UTC

Exploit probability

1.6% · EPSS, next 30 days

Weakness

CWE-121

Record status

Modified

Affected

• Messagepack < 1.9.3
• Messagepack < 2.1.80
• Messagepack 2.0.94
• Messagepack 2.0.110
• Messagepack 2.0.119
• Messagepack 2.0.123
• Messagepack 2.0.204
• Messagepack 2.0.270

Attack profile CVSS 3.1 · 4.8

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2020-5234.md and follow it. Check whether this project is affected by CVE-2020-5234. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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