CVE-2021-21284 · cross-distro fix matrix

CVE-2021-21284: 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

Affects 8 Linux releases across 8 (distro × package) combinations.

Fix per ecosystem

Each block below is a distro release where CVE-2021-21284 has a known fix. Run the listed command on that distro to remediate.

Debian bullseye

Source: Debian Security Tracker

docker.io→ fixed in20.10.3+dfsg1-1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y docker.io
```

Debian bookworm

Source: Debian Security Tracker

docker.io→ fixed in20.10.3+dfsg1-1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y docker.io
```

Debian trixie

Source: Debian Security Tracker

docker.io→ fixed in20.10.3+dfsg1-1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y docker.io
```

Alpine v3.20

Source: Alpine secdb

docker→ fixed in20.10.3-r0
```
apk update && apk add --upgrade docker
```

Alpine v3.21

Source: Alpine secdb

docker→ fixed in20.10.3-r0
```
apk update && apk add --upgrade docker
```

Alpine edge

Source: Alpine secdb

docker→ fixed in20.10.3-r0
```
apk update && apk add --upgrade docker
```

Alpine v3.18

Source: Alpine secdb

docker→ fixed in20.10.3-r0
```
apk update && apk add --upgrade docker
```

Alpine v3.19

Source: Alpine secdb

docker→ fixed in20.10.3-r0
```
apk update && apk add --upgrade docker
```

Are YOU affected by CVE-2021-21284?

5-second check on your actual server. Reads /etc/os-release, uname -r, and the distro's package manager; matches against this same cross-source index live.

curl https://mindsparkstack.com/scan.sh | bash

Form-based quickscan View on NVD

Continuous monitoring beats manual checking

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