moby Access to remapped root allows privilege escalation to real root
Date: 2024-01
Affected: go/github.com/moby/moby, go/github.com/moby/moby
Attack vector: path-traversal
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2021-21284
CWE: CWE-22
CVSS: 6.8 (CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N)

### Impact When using `--userns-remap`, if the root user in the remapped namespace has access to the host filesystem they can modify files under `/var/lib/docker/<remapping>` that cause writing files with extended privileges. ### Patches Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user. ### Credits Maintainers would like to thank Alex Chapman for discovering the vulnerability; @awprice, @nathanburrell, @raulgomis, @chris-walz, @erin-jensby, @bassmatt, @mark-adams, @dbaxa for working on it and Zac Ellis for responsibly disclosing it to security@docker.com


Mitigations:

Architectural layers (MAESTRO):