CVE-2021-21284: privilege escalation in Moby
First published: Tue Feb 02 2021(Updated: )
### 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
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/docker.io | 18.09.1+dfsg1-7.1+deb10u3 20.10.5+dfsg1-1+deb11u2 20.10.24+dfsg1-1 20.10.25+dfsg1-2 | |
| go/github.com/moby/moby | >=20.10.0-beta1<20.10.3 | 20.10.3 |
| go/github.com/moby/moby | <19.3.15 | 19.3.15 |
| IBM InfoSphere Guardium z/OS | <=10.5 | |
| IBM InfoSphere Guardium z/OS | <=10.6 | |
| IBM InfoSphere Guardium z/OS | <=11.0 | |
| IBM InfoSphere Guardium z/OS | <=11.1 | |
| IBM InfoSphere Guardium z/OS | <=11.2 | |
| IBM InfoSphere Guardium z/OS | <=11.3 | |
| Python Docker | <19.03.15 | |
| Python Docker | >=20.0.0<20.10.3 | |
| Debian Linux | =10.0 | |
| NetApp E-Series SANtricity OS Controller | >=11.0.0<=11.60.3 |
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Reference Links
- https://docs.docker.com/engine/release-notes/#20103
- https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c
- https://github.com/moby/moby/releases/tag/v19.03.15
- https://github.com/moby/moby/releases/tag/v20.10.3
- https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc
- https://security.gentoo.org/glsa/202107-23
- https://security.netapp.com/advisory/ntap-20210226-0005/
- https://www.debian.org/security/2021/dsa-4865
- https://github.com/moby/moby/commit/1342c51d5e809d2994e6f7e490c8d2b3b12c28ae
- https://github.com/moby/moby/commit/5eff67a2c294b7e72607e0949ebc0de21710e4d3
- https://github.com/moby/moby/commit/67de83e70bca92ae6a08e28a03b3fc8fcca9f3f1
- https://security-tracker.debian.org/tracker/CVE-2021-21284
- https://exchange.xforce.ibmcloud.com/vulnerabilities/196047
- https://www.ibm.com/support/pages/node/6455281 (Advisory)
- https://nvd.nist.gov/vuln/detail/CVE-2021-21284
- https://github.com/advisories/GHSA-7452-xqpj-6rpc (Advisory)
- https://security.netapp.com/advisory/ntap-20210226-0005
Frequently Asked Questions
What is the vulnerability ID for this Docker vulnerability?
The vulnerability ID for this Docker vulnerability is CVE-2021-21284.
What versions of Docker are affected by this vulnerability?
Versions before 9.03.15 and 20.10.3 of Docker are affected by this vulnerability.
What is the impact of this vulnerability?
This vulnerability allows privilege escalation to real root if the root user in the remapped namespace has access to the host filesystem.
How can I fix this vulnerability?
To fix this vulnerability, update Docker to version 9.03.15 or 20.10.3.
Where can I find more information about this vulnerability?
More information about this vulnerability can be found in the following references: [GitHub Advisory](https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc), [GitHub Commit 1](https://github.com/moby/moby/commit/1342c51d5e809d2994e6f7e490c8d2b3b12c28ae), [GitHub Commit 2](https://github.com/moby/moby/commit/5eff67a2c294b7e72607e0949ebc0de21710e4d3).
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