ubuntu-cve-2021-21284
Vulnerability from osv_ubuntu
Published
2021-02-02 18:15
Modified
2025-09-08 16:46
Summary
Details
In Docker before versions 9.03.15, 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/" that cause writing files with extended privileges. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.
Severity
6.8 (Medium)
6.8 (Medium)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "docker.io",
"binary_version": "18.09.7-0ubuntu1~16.04.9+esm2"
},
{
"binary_name": "golang-docker-dev",
"binary_version": "18.09.7-0ubuntu1~16.04.9+esm2"
},
{
"binary_name": "golang-github-docker-docker-dev",
"binary_version": "18.09.7-0ubuntu1~16.04.9+esm2"
},
{
"binary_name": "vim-syntax-docker",
"binary_version": "18.09.7-0ubuntu1~16.04.9+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "docker.io",
"purl": "pkg:deb/ubuntu/docker.io@18.09.7-0ubuntu1~16.04.9+esm2?arch=source\u0026distro=esm-infra/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.6.2~dfsg1-1ubuntu4",
"1.10.2-0ubuntu3",
"1.10.2-0ubuntu4",
"1.10.3-0ubuntu1",
"1.10.3-0ubuntu4",
"1.10.3-0ubuntu5",
"1.10.3-0ubuntu6",
"1.11.2-0ubuntu5~16.04",
"1.12.1-0ubuntu13~16.04.1",
"1.12.3-0ubuntu4~16.04.2",
"1.12.6-0ubuntu1~16.04.1",
"1.13.1-0ubuntu1~16.04.2",
"17.03.2-0ubuntu2~16.04.1",
"18.06.1-0ubuntu1~16.04.2",
"18.06.1-0ubuntu1.2~16.04.1",
"18.09.2-0ubuntu1~16.04.1",
"18.09.5-0ubuntu1~16.04.2",
"18.09.7-0ubuntu1~16.04.1",
"18.09.7-0ubuntu1~16.04.4",
"18.09.7-0ubuntu1~16.04.5",
"18.09.7-0ubuntu1~16.04.6",
"18.09.7-0ubuntu1~16.04.7",
"18.09.7-0ubuntu1~16.04.9+esm1",
"18.09.7-0ubuntu1~16.04.9+esm2"
]
},
{
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "docker.io",
"binary_version": "20.10.7-0ubuntu1~18.04.1"
},
{
"binary_name": "golang-docker-dev",
"binary_version": "20.10.7-0ubuntu1~18.04.1"
},
{
"binary_name": "golang-github-docker-docker-dev",
"binary_version": "20.10.7-0ubuntu1~18.04.1"
},
{
"binary_name": "vim-syntax-docker",
"binary_version": "20.10.7-0ubuntu1~18.04.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "docker.io",
"purl": "pkg:deb/ubuntu/docker.io@20.10.7-0ubuntu1~18.04.1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "20.10.7-0ubuntu1~18.04.1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.13.1-0ubuntu6",
"17.03.2-0ubuntu1",
"17.03.2-0ubuntu3",
"17.03.2-0ubuntu5",
"17.12.1-0ubuntu1",
"18.06.1-0ubuntu1~18.04.1",
"18.06.1-0ubuntu1.2~18.04.1",
"18.09.2-0ubuntu1~18.04.1",
"18.09.5-0ubuntu1~18.04.2",
"18.09.7-0ubuntu1~18.04.1",
"18.09.7-0ubuntu1~18.04.3",
"18.09.7-0ubuntu1~18.04.4",
"19.03.6-0ubuntu1~18.04.1",
"19.03.6-0ubuntu1~18.04.2",
"19.03.6-0ubuntu1~18.04.3",
"20.10.2-0ubuntu1~18.04.2",
"20.10.2-0ubuntu1~18.04.3"
]
},
{
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "docker.io",
"binary_version": "20.10.7-0ubuntu1~20.04.1"
},
{
"binary_name": "golang-docker-dev",
"binary_version": "20.10.7-0ubuntu1~20.04.1"
},
{
"binary_name": "golang-github-docker-docker-dev",
"binary_version": "20.10.7-0ubuntu1~20.04.1"
},
{
"binary_name": "vim-syntax-docker",
"binary_version": "20.10.7-0ubuntu1~20.04.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "docker.io",
"purl": "pkg:deb/ubuntu/docker.io@20.10.7-0ubuntu1~20.04.1?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "20.10.7-0ubuntu1~20.04.1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"19.03.2-0ubuntu1",
"19.03.6-0ubuntu1",
"19.03.8-0ubuntu1",
"19.03.8-0ubuntu1.20.04",
"19.03.8-0ubuntu1.20.04.1",
"19.03.8-0ubuntu1.20.04.2",
"20.10.2-0ubuntu1~20.04.2",
"20.10.2-0ubuntu1~20.04.3"
]
}
],
"aliases": [],
"details": "In Docker before versions 9.03.15, 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/\u003cremapping\u003e\" that cause writing files with extended privileges. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.",
"id": "UBUNTU-CVE-2021-21284",
"modified": "2025-09-08T16:46:57Z",
"published": "2021-02-02T18:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-21284"
},
{
"type": "REPORT",
"url": "https://github.com/moby/moby/security/advisories/GHSA-7452-xqpj-6rpc"
},
{
"type": "REPORT",
"url": "https://docs.docker.com/engine/release-notes/#20103"
},
{
"type": "REPORT",
"url": "https://github.com/moby/moby/commit/64bd4485b3a66a597c02c95f5776395e540b2c7c"
},
{
"type": "REPORT",
"url": "https://github.com/moby/moby/releases/tag/v19.03.15"
},
{
"type": "REPORT",
"url": "https://github.com/moby/moby/releases/tag/v20.10.3"
},
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-5032-1"
},
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-5032-2"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-21284"
}
],
"related": [
"USN-5032-1",
"USN-5032-2"
],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-21284"
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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