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containerd-shim API Exposed to Host Network Containers

Moderate severity GitHub Reviewed Published Nov 30, 2020 in containerd/containerd • Updated Oct 2, 2023

Package

gomod github.com/containerd/containerd (Go)

Affected versions

< 1.3.9
>= 1.4.0, < 1.4.3

Patched versions

1.3.9
1.4.3

Description

Impact

Access controls for the shim’s API socket verified that the connecting process had an effective UID of 0, but did not otherwise restrict access to the abstract Unix domain socket. This would allow malicious containers running in the same network namespace as the shim, with an effective UID of 0 but otherwise reduced privileges, to cause new processes to be run with elevated privileges.

Specific Go Packages Affected

github.com/containerd/containerd/cmd

Patches

This vulnerability has been fixed in containerd 1.3.9 and 1.4.3. Users should update to these versions as soon as they are released. It should be noted that containers started with an old version of containerd-shim should be stopped and restarted, as running containers will continue to be vulnerable even after an upgrade.

Workarounds

If you are not providing the ability for untrusted users to start containers in the same network namespace as the shim (typically the "host" network namespace, for example with docker run --net=host or hostNetwork: true in a Kubernetes pod) and run with an effective UID of 0, you are not vulnerable to this issue.

If you are running containers with a vulnerable configuration, you can deny access to all abstract sockets with AppArmor by adding a line similar to deny unix addr=@**, to your policy.

It is best practice to run containers with a reduced set of privileges, with a non-zero UID, and with isolated namespaces. The containerd maintainers strongly advise against sharing namespaces with the host. Reducing the set of isolation mechanisms used for a container necessarily increases that container's privilege, regardless of what container runtime is used for running that container.

Credits

The containerd maintainers would like to thank Jeff Dileo of NCC Group for responsibly disclosing this issue in accordance with the containerd security policy and for reviewing the patch.

For more information

If you have any questions or comments about this advisory:

References

@dmcgowan dmcgowan published to containerd/containerd Nov 30, 2020
Published by the National Vulnerability Database Dec 1, 2020
Reviewed May 21, 2021
Published to the GitHub Advisory Database May 24, 2021
Last updated Oct 2, 2023

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
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
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:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS score

0.045%
(17th percentile)

Weaknesses

CVE ID

CVE-2020-15257

GHSA ID

GHSA-36xw-fx78-c5r4

Source code

No known source code

Credits

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