Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2021-32635: 1.42% estimated exploitation activity in the next 30 days; percentile 72.78 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Due 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. Patches All users should upgrade to Singularity 3.7.4 or later. A patch was applied at: https://github.com/sylabs/singularity/commit/d52ae9d13979733c5e987a566fae59ed6f1bf796 Workarounds Users who only interact with the default remote endpoint are not affected. Installations with an execution control list configured to restrict execution to…

Published by the source

1 Jun 2021, 21:21 UTC

Last modified by the source

3 Feb 2023, 05:00 UTC

Source last checked

26 Oct 2026, 14:55 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5mv9-q7fq-9394

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# Patch Next advisory brief: CVE-2021-32635

Advisory: Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint
IDs: CVE-2021-32635, GHSA-5mv9-q7fq-9394
Record: https://patchnext.com/advisories/cve-2021-32635 (revision 1, source checked 26 Oct 2026, 14:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/sylabs/singularity 3.7.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/sylabs/singularity: affected >= 3.7.2, < 3.7.4; fixed in 3.7.4

## Suggested inspection (read-only)
- Go github.com/sylabs/singularity: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/sylabs/singularity.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5mv9-q7fq-9394 (GitHub-reviewed advisory GHSA-5mv9-q7fq-9394 lists affected ranges: Go github.com/sylabs/singularity >=3.7.2 <3.7.4)

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