Application crash via unbounded LZ4 decompression reads
Published Jun 22, 2026 · Updated Jun 22, 2026
Out-of-bounds reads in MessagePack for C# before 2.5.301 and 3.0.214-rc.1 through 3.1.6 allow remote attackers to crash applications. The optional Lz4Block and Lz4BlockArray decoder uses a deprecated fast-decompression routine without a source-length bound, so manipulated token and length fields drive reads beyond the compressed input buffer. Exploitation requires an application to deserialize untrusted MessagePack data with LZ4 compression enabled; failure terminates the process, and an over-read can disclose limited adjacent memory before termination.
Summary
What happened
Out-of-bounds reads in MessagePack for C# before 2.5.301 and 3.0.214-rc.1 through 3.1.6 allow remote attackers to crash applications. The optional Lz4Block and Lz4BlockArray decoder uses a deprecated fast-decompression routine without a source-length bound, so manipulated token and length fields drive reads beyond the compressed input buffer. Exploitation requires an application to deserialize untrusted MessagePack data with LZ4 compression enabled; failure terminates the process, and an over-read can disclose limited adjacent memory before termination.
The record
- CVE
- CVE-2026-48109
- Published
- Jun 22, 2026
- Updated
- Jun 22, 2026
- Vendor
- MessagePack-CSharp
- Product
- MessagePack for C#
- Classifications
- CWE-20, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 22, 2026CVE publishedPublication date reported by the CVE source.
- Jun 22, 2026Record 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.
- Affected versionversion=< 2.5.301
- Affected versionversion=>= 3.1.7, < 3.1.7
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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