# CVE-2026-54522: ruby-msgpack: MessagePack for Ruby is an implementation of the MessagePack binary serialization format

CVE-2026-54522 is fixed in ruby-msgpack on 1 platform by DEBIAN-CVE-2026-54522 (version 1.8.3-1), released July 31, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-54522
- Priority: Routine
- CVSS: 5.4 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 30, 2026

## Description

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ruby-msgpack Debian 14 | 1.8.3-1 | [DEBIAN-CVE-2026-54522](https://patchblox.com/security/data/fix/linux/debian-cve-2026-54522.md) | Jul 31, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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