GHSA-3fwx-pjgw-3558 CVE-2021-41091 GO-2024-2500
Moby (Docker Engine) Insufficiently restricted permissions on data directory
- Severity
- 5.9 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 2.85%
- Chance of exploitation in the next 30 days. Higher than 86.70% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-281 Improper Preservation of Permissions
- CWE-732 Incorrect Permission Assignment for Critical Resource
- Fix
- Available
- 2 packages have a fixed version
Description
Impact
A bug was found in Moby (Docker Engine) where the data directory (typically /var/lib/docker) contained subdirectories with insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs. When containers included executable programs with extended permission bits (such as setuid), unprivileged Linux users could discover and execute those programs. When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files.
Patches
This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers should be stopped and restarted for the permissions to be fixed.
Workarounds
Limit access to the host to trusted users. Limit access to host volumes to trusted containers.
Credits
The Moby project would like to thank Joan Bruguera for responsibly disclosing this issue in accordance with the Moby security policy.
For more information
If you have any questions or comments about this advisory:
- Open an issue
- Email us at security@docker.com if you think you’ve found a security bug
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/docker/docker | < 20.10.9 |
20.10.9 |
| github.com/docker/docker | < 20.10.9+incompatible |
20.10.9+incompatible |
| github.com/moby/moby | < 20.10.9 |
20.10.9 |
| github.com/moby/moby | < 20.10.9+incompatible |
20.10.9+incompatible |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/docker/docker Go → 20.10.9
- go
go get github.com/docker/docker@v20.10.9 && go mod tidy
github.com/moby/moby Go → 20.10.9
- go
go get github.com/moby/moby@v20.10.9 && go mod tidy
Severity breakdown
CVSS 3.1 5.9
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
Weakness
CWE-281: Improper Preservation of Permissions
The product does not preserve permissions or incorrectly preserves permissions when copying, restoring, or sharing objects, which can cause them to have less restrictive permissions than intended.
CWE-732: Incorrect Permission Assignment for Critical Resource
The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.
How to prevent it
- Implementation: When using a critical resource such as a configuration file, check to see if the resource has insecure permissions (such as being modifiable by any regular user) [REF-62], and generate an error or even exit the software if there is a possibility that the resource could have been modified by an unauthorized party.
- Architecture and Design: Divide the software into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully defining distinct user groups, privileges, and/or roles. Map these against data, functionality, and the related resources. Then set the permissions accordingly. This will allow you to maintain more fine-grained control over your resources. [REF-207]
- Architecture and Design, Operation: Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Implementation, Installation: During program startup, explicitly set the default permissions or umask to the most restrictive setting possible. Also set the appropriate permissions during program installation. This will prevent you from inheriting insecure permissions from any user who installs or runs the program.
- System Configuration: For all configuration files, executables, and libraries, make sure that they are only readable and writable by the software's administrator.
- Documentation: Do not suggest insecure configuration changes in documentation, especially if those configurations can extend to resources and other programs that are outside the scope of the application.
- Installation: Do not assume that a system administrator will manually change the configuration to the settings that are recommended in the software's manual.
- Operation, System Configuration: Ensure that the software runs properly under the United States Government Configuration Baseline (USGCB) [REF-199] or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software.
- Implementation, System Configuration, Operation: When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.
References
Advisories
Packages
Other links
- github.com/moby/moby/security/advisories/GHSA-3fwx-pjgw-3558
- github.com/moby/moby/commit/f0ab919f518c47240ea0e72d0999576bb8008e64
- cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/B5Q6G…
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZNFAD…
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-rg2x-37c3-w2rh Docker: Race condition in docker cp allows bind mount redirection to host path | High | Also affects github.com/docker/docker |
| GHSA-vp62-88p7-qqf5 Docker: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap | Medium | Also affects github.com/docker/docker |
| GHSA-x86f-5xw2-fm2r Docker: `PUT /containers/{id}/archive` executes container binary on the host | High | Also affects github.com/docker/docker |
| GO-2026-4887 Moby has AuthZ plugin bypass when provided oversized request bodies | High | Also affects github.com/docker/docker |
| GHSA-pxq6-2prw-chj9 Moby has an Off-by-one error in its plugin privilege validation | High | Also affects github.com/docker/docker |
| GHSA-4vq8-7jfc-9cvp Moby firewalld reload removes bridge network isolation | Medium | Also affects github.com/docker/docker |
| GHSA-x4rx-4gw3-53p4 Moby firewalld reload makes published container ports accessible from remote hosts | Medium | Also affects github.com/docker/docker |
| GHSA-v23v-6jw2-98fq Authz zero length regression | Critical | Also affects github.com/docker/docker |
Credits: Joan Bruguera
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