Bug 1924740 (CVE-2021-21284) - CVE-2021-21284 docker: access to remapped root allows privilege escalation to real root
Summary: CVE-2021-21284 docker: access to remapped root allows privilege escalation to...
Keywords:
Status: CLOSED WONTFIX
Alias: CVE-2021-21284
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1934044 1934045
Blocks: 1924746
TreeView+ depends on / blocked
 
Reported: 2021-02-03 14:33 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-10-28 11:25 UTC (History)
13 users (show)

Fixed In Version: docker 19.03.15, docker 20.10.3
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the `userns-remap` feature of Docker. The root user in the remapped namespace can modify files under /var/lib/docker/<remapping>, leading to possible privilege escalation to the root user in the host. The highest threat from this vulnerability is to data integrity.
Clone Of:
Environment:
Last Closed: 2021-10-28 11:24:06 UTC


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Description Guilherme de Almeida Suckevicz 2021-02-03 14:33:41 UTC
In Docker before versions 19.03.15, 20.10.3 there is a vulnerability involving the --userns-remap option in which access to remapped root allows privilege escalation to real root. 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. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.

Comment 1 Mauro Matteo Cascella 2021-02-19 14:55:00 UTC
External References:

https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc

Comment 4 Mauro Matteo Cascella 2021-03-03 16:10:17 UTC
Support for user namespaces (--userns-remap) was introduced in Docker-1.10.0: https://docs.docker.com/engine/release-notes/prior-releases/#security-6.


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