CVE-2021-32635: Singularity is an open source container platform. In verions 3.7.2 and 3.7.3, Dde to incorrect use of a default URL, `singularity` action commands (`r...

Description

Singularity is an open source container platform. In verions 3.7.2 and 3.7.3, Dde to incorrect use of a default URL, `singularity` action commands (`run`/`shell`/`exec`) specifying a container using a `library://` URI will always attempt to retrieve the container from the default remote endpoint (`cloud.sylabs.io`) rather than the configured remote endpoint. An attacker may be able to push a malicious container to the default remote endpoint with a URI that is identical to the URI used by a victim with a non-default remote endpoint, thus executing the malicious container. Only action commands (`run`/`shell`/`exec`) against `library://` URIs are affected. Other commands such as `pull` / `push` respect the configured remote endpoint. The vulnerability is patched in Singularity version 3.7.4. Two possible workarounds exist: Users can only interact with the default remote endpoint, or an installation can have an execution control list configured to restrict execution to containers signed with specific secure keys.

Metrics

CVSS 3.1

6.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L

EPSS Probability

1.42%

69.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Sylabs	Singularity	3.7.2
Sylabs	Singularity	3.7.3

References

https://github.com/sylabs/singularity/releases/tag/v3.7.4Third Party Advisory
https://github.com/sylabs/singularity/security/advisories/GHSA-5mv9-q7fq-9394Third Party Advisory
https://security.gentoo.org/glsa/202107-50Third Party Advisory
https://github.com/sylabs/singularity/releases/tag/v3.7.4Third Party Advisory
https://github.com/sylabs/singularity/security/advisories/GHSA-5mv9-q7fq-9394Third Party Advisory
https://security.gentoo.org/glsa/202107-50Third Party Advisory

Timeline

Published: May 28, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-32635?

Singularity is an open source container platform. In verions 3.7.2 and 3.7.3, Dde to incorrect use of a default URL, `singularity` action commands (`run`/`shell`/`exec`) specifying a container using a `library://` URI will always attempt to retrieve the container from the default remote endpoint (`cloud.sylabs.io`) rather than the configured remote endpoint. An attacker may be able to push a malicious container to the default remote endpoint with a URI that is identical to the URI used by a victim with a non-default remote endpoint, thus executing the malicious container. Only action commands (`run`/`shell`/`exec`) against `library://` URIs are affected. Other commands such as `pull` / `push` respect the configured remote endpoint. The vulnerability is patched in Singularity version 3.7.4. Two possible workarounds exist: Users can only interact with the default remote endpoint, or an installation can have an execution control list configured to restrict execution to containers signed with specific secure keys.

How severe is CVE-2021-32635?

CVE-2021-32635 has a CVSS score of 6.3/10 (MEDIUM severity). The EPSS model estimates a 1.42% probability of exploitation in the next 30 days.

How do I fix CVE-2021-32635?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.