CVE-2020-5234Network attack vector

Process crash or CPU exhaustion via unsafe deserialization

Published Jan 31, 2020 · Updated Aug 4, 2024

Denial of service in MessagePack for C# packages before 1.9.11 and 2.0.0 through 2.1.89 allows attackers to crash or exhaust a process. Built-in and custom formatters omit bounded-depth handling for nested objects and collision-resistant comparers for attacker-controlled hash keys. Reachability requires an application to deserialize untrusted MessagePack data; deep object graphs crash the process, while colliding keys consume excessive CPU.

CVSS severity4.8
Medium
EPSS probability1.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in MessagePack for C# packages before 1.9.11 and 2.0.0 through 2.1.89 allows attackers to crash or exhaust a process. Built-in and custom formatters omit bounded-depth handling for nested objects and collision-resistant comparers for attacker-controlled hash keys. Reachability requires an application to deserialize untrusted MessagePack data; deep object graphs crash the process, while colliding keys consume excessive CPU.

The record

CVE
CVE-2020-5234
Published
Jan 31, 2020
Updated
Aug 4, 2024
Vendor
MessagePack-CSharp
Product
MessagePack.ReactiveProperty
Classifications
CWE-787, CWE-121, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 31, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.9.11
  2. Affected versionversion=>= 2.0.0, < 2.1.90

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MessagePack-CSharp · MessagePack.ReactivePropertyversion=< 1.9.11; version=>= 2.0.0, < 2.1.90
MessagePack-CSharp · MessagePack for C#version=< 1.9.11; version=>= 2.0.0, < 2.1.90
MessagePack-CSharp · MessagePack.ImmutableCollectionversion=< 1.9.11; version=>= 2.0.0, < 2.1.90
MessagePack-CSharp · MessagePack.UnityShimsversion=< 1.9.11; version=>= 2.0.0, < 2.1.90

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.8GitHubCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-121Stack-based Buffer Overflow
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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