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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-48109

31
FAUCET Score

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.

First published: Jun 22, 2026Last modified: Jun 22, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 2.5.301CPE matchmatch criteria
cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*
>= 3.0.3, < 3.1.7CPE matchmatch criteria
cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*

CVSS Data

CVSS version used by this source: 3.1

8.2HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
4.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.51%
Probability of exploitation in next 30 days
EPSS Percentile
40.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0051 is in the 18th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

nugetpatch availablevia ghsa
Product: MessagePackFixed in: 2.5.301
nugetpatch availablevia ghsa
Product: MessagePackFixed in: 3.1.7
github_advisoryworkaround availablevia nvd_reference
View patch

Vendor Advisories (1)

nugetGHSA-hv8m-jj95-wg3xhigh

MessagePack's LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input

Jun 11, 2026

References

github.com / MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-hv8m-jj95-wg3x
MitigationVendor Advisory