CVE-2021-32635
MEDIUMCVE-2021-32635 is a medium-severity (CVSS 6.3) Improper Input Validation vulnerability in github.com/sylabs/singularity. O3 Security confirms whether CVE-2021-32635 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint
Blast Radius
github.com/sylabs/singularityReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sylabs/singularity | ≥ 3.7.2&&< 3.7.4 | 3.7.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sylabs/singularity. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/sylabs/singularity to 3.7.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32635 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-32635 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-32635. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-32635 in your dependencies?
O3 detects CVE-2021-32635 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.