PatchTheCEVCVE-2026-54522: MessagePack for Ruby is an implementation of the MessagePack binary serialization format
27
Routine
MEDIUM 5.4UPGRADE
CVE-2026-54522 is a medium-severity flaw (CVSS 5.4) affecting messagepack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- Public exploit reference
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.4 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | Low |
| User interaction | None |
| EPSS exploit chance | 0.2% (top 87%) |
| CISA exploited list | No |
| Weakness | CWE-416 |
| Published | 2026-07-30 |
| Last modified | 2026-10-23 |
Publisher (CNA): GitHub, Inc. · Vendor: msgpack
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
msgpack messagepack UPGRADE
Affected: < 1.8.2
Fixed in: 1.8.2
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy messagepack || rpm -q messagepack || messagepack --version
2. UPGRADE to 1.8.2 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade messagepack
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade messagepack
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.