Vulnerability · Published Jun 30, 2026 · Assigned by GitHub_M
CVE-2026-57585MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error
High 7.5
In plain English
A high-severity use-after-free in msgpack-python from msgpack. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack. If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | python-msgpack | no fix listed | DEBIAN-CVE-2026-57585 |
| Debian:13 | python-msgpack | no fix listed | DEBIAN-CVE-2026-57585 |
| Debian:14 | python-msgpack | 1.1.2-3 | DEBIAN-CVE-2026-57585 |
| PyPI | msgpack | 1.2.1 | GHSA-6v7p-g79w-8964 |
| PyPI | msgpack | 1.2.1 | PYSEC-2026-3625 |
| Ubuntu:22.04:LTS | python-msgpack | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:24.04:LTS | python-msgpack | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:25.10 | python-msgpack | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:26.04:LTS | python-msgpack | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:26.10 | python-msgpack | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:25.10 | python-pip | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:26.10 | python-pip | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:24.04:LTS | python-srsly | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:25.10 | python-srsly | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:26.04:LTS | python-srsly | no fix listed | UBUNTU-CVE-2026-57585 |
| Ubuntu:26.10 | python-srsly | no fix listed | UBUNTU-CVE-2026-57585 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| msgpack | msgpack-python | < 1.2.1 |
Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H