CVE-2026-48510GHSA-V72X-2H86-7F8M
MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 3.1.7, 2.5.301
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
CISA's decision points: whether it is exploited, whether attacks can be automated, and how much control an attacker gets. Assessed (SSVC 2.0.3).What do these mean? →
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, when MessagePack-CSharp decompresses Lz4Block or Lz4BlockArray payloads, it reads declared uncompressed lengths from the wire and allocates output buffers based on those lengths before validating that the compressed data is valid or that the declared expansion is reasonable. A small payload can claim a very large uncompressed length and force a large allocation before LZ4 decoding begins. This vulnerability is fixed in 2.5.301 and 3.1.7.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- MessagePack-CSharp MessagePack-CSharp
From 3.0 · fixed in 3.1.7; fixed in 2.5.301
- MessagePackNuGet
fixed in 2.5.301
- MessagePackNuGet
From 3.0 · fixed in 3.1.7