CVE-2020-5234 | Untrusted data can lead to DoS attack in MessagePack for C# and Unity

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.

Published: 2020-01-31 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-5234 is rated Moderate Risk (45.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.58%). EPSS rose +1.03% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-5234

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.55% 1.58% +1.03%
2 2026-05-07 0.58% 0.55% -0.03%
3 2025-11-21 — 0.58% —

Full EPSS history (17 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-5234

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.2 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.0 6.9 [email protected]

Weakness enumeration for CVE-2020-5234

GitHub Security Advisory for CVE-2020-5234

GHSA-7q36-4xx7-xcxf · Severity: medium · Ecosystem: nuget — Untrusted data can lead to DoS attack due to hash collisions and stack overflow in MessagePack

Affected software / configurations for CVE-2020-5234

Vendor Product Version Raw CPE
messagepack messagepack < 1.9.3 cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*
messagepack messagepack >= 2.0.323, < 2.1.80 cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*
messagepack messagepack 2.0.94 cpe:2.3:a:messagepack:messagepack:2.0.94:alpha:*:*:*:c\#:*:*
messagepack messagepack 2.0.110 cpe:2.3:a:messagepack:messagepack:2.0.110:alpha:*:*:*:c\#:*:*
messagepack messagepack 2.0.119 cpe:2.3:a:messagepack:messagepack:2.0.119:beta:*:*:*:c\#:*:*
messagepack messagepack 2.0.123 cpe:2.3:a:messagepack:messagepack:2.0.123:beta:*:*:*:c\#:*:*
messagepack messagepack 2.0.204 cpe:2.3:a:messagepack:messagepack:2.0.204:beta:*:*:*:c\#:*:*
messagepack messagepack 2.0.270 cpe:2.3:a:messagepack:messagepack:2.0.270:rc:*:*:*:c\#:*:*
messagepack messagepack 2.0.299 cpe:2.3:a:messagepack:messagepack:2.0.299:rc:*:*:*:c\#:*:*

References for CVE-2020-5234

cvelogic Threat Intelligence