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moby Access to remapped root allows privilege escalation to real root

Moderate severity GitHub Reviewed Published Feb 2, 2021 in moby/moby • Updated Jun 10, 2024

Package

gomod github.com/moby/moby (Go)

Affected versions

< 19.3.15
>= 20.10.0-beta1, < 20.10.3

Patched versions

19.3.15
20.10.3

Description

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

References

@tiborvass tiborvass published to moby/moby Feb 2, 2021
Published by the National Vulnerability Database Feb 2, 2021
Published to the GitHub Advisory Database Jan 31, 2024
Reviewed Jan 31, 2024
Last updated Jun 10, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

EPSS score

0.047%
(19th percentile)

Weaknesses

CVE ID

CVE-2021-21284

GHSA ID

GHSA-7452-xqpj-6rpc

Source code

No known source code

Credits

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