Summary
Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint
Workarounds
Users who only interact with the default remote endpoint are not affected.
Installations with an execution control list configured to restrict execution to containers signed with specific secure keys are not affected.
For more information
General questions about the impact of the advisory can be asked in the:
Any sensitive security concerns should be directed to: [email protected]
See our Security Policy here: https://sylabs.io/security-policy
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.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2021-32635 has a CVSS score of 6.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.7.4); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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All users should upgrade to Singularity 3.7.4 or later.
A patch was applied at: https://github.com/sylabs/singularity/commit/d52ae9d13979733c5e987a566fae59ed6f1bf796
Frequently Asked Questions
- What is CVE-2021-32635? CVE-2021-32635 is a medium-severity improper input validation vulnerability in github.com/sylabs/singularity (go), affecting versions >= 3.7.2, < 3.7.4. It is fixed in 3.7.4. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2021-32635? CVE-2021-32635 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/sylabs/singularity are affected by CVE-2021-32635? github.com/sylabs/singularity (go) versions >= 3.7.2, < 3.7.4 is affected.
- Is there a fix for CVE-2021-32635? Yes. CVE-2021-32635 is fixed in 3.7.4. Upgrade to this version or later.
- Is CVE-2021-32635 exploitable, and should I be worried? Whether CVE-2021-32635 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-32635 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-32635? Upgrade
github.com/sylabs/singularityto 3.7.4 or later.