CVE-2025-64750

Workarounds

There are no known workarounds, other than to define system-wide apparmor / selinux policy for Singularity itself. This would apply to all containers, not just those run with the --security flags. Additionally, restrictions that are reasonable to apply to container processes may impact the functionality of Singularity.

References

Related vulnerabilities in runc:

• runc CVE-2025-52881
• runc CVE-2019-19921

Native Mode (default)

Singularity's default native runtime allows users to apply restrictions to container processes using the apparmor or selinux Linux Security Modules (LSMs), via the --security selinux:<label> or --security apparmor:<profile> flags.

LSM labels are written to process or thread attrs/exec under /proc. If a user relies on LSM restrictions to prevent malicious operations then, under certain circumstances, an attacker can redirect the LSM label write operation so that it is ineffective. This requires:

• The attacker to cause the user to run a malicious container image that redirects the mount of /proc to the destination of a shared mount, either known to be configured on the target system, or that will be specified by the user when running the container.
• Control of the content of the shared mount, for example through another malicious container which also binds it, or as a user with relevant permissions on the host system it is bound from.

Note that Singularity does not attempt to prevent damaging operations, or container escape, from containers that are started as the host root user. When a non-root user starts a container any LSM writes to /proc are performed as that user. For these reasons, the denial-of-service and container escape attacks detailed in runc CVE-2025-52881 are not relevant. Processes running in non-root containers are subject to the standard permissions for the non-root account used, and cannot escalate privilege, even when intended container-specific LSM labels are not correctly applied.

In addition, a bug in the detection of selinux support in Singularity's default setuid flow means that --security selinux:<label> flags may not be applied, even in the absence of an attack - but in this case a warning message is emitted, indicating that selinux is unavailable. This warning may be may be overlooked, mis-interpreted, or not seen when singularity is run from a script or other tool. Failure to apply requested restrictions should result in a fatal error, rather than a warning message.

OCI-Mode

Singularity's OCI-mode is unaffected as it does not currently support applying LSM restrictions via the --security flag.

CVE-2025-64750 has a CVSS score of 4.5 (Medium). The vector is requires local access, 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 (4.3.5, 4.1.11); upgrading removes the vulnerable code path.

Kodem intelligence

Ineffective write of selinux process labels is addressed via an update to the containers/selinux dependency in https://github.com/sylabs/singularity/pull/3850. This update brings in the upstream fix for CVE-2025-52881 in this dependency.

Ineffective write of apparmor process labels is addressed in commit 5af3e79.

Failure to detect apparmor / selinux support, when --security flags are provided, is made an error rather than a warning in commit 2788296.

1. What is CVE-2025-64750? CVE-2025-64750 is a medium-severity security vulnerability in github.com/sylabs/singularity/v4 (go), affecting versions >= 4.2.0-rc.1, < 4.3.5. It is fixed in 4.3.5, 4.1.11.
2. How severe is CVE-2025-64750? CVE-2025-64750 has a CVSS score of 4.5 (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.
3. Which versions of github.com/sylabs/singularity/v4 are affected by CVE-2025-64750? github.com/sylabs/singularity/v4 (go) versions >= 4.2.0-rc.1, < 4.3.5 is affected.
4. Is there a fix for CVE-2025-64750? Yes. CVE-2025-64750 is fixed in 4.3.5, 4.1.11. Upgrade to this version or later.
5. Is CVE-2025-64750 exploitable, and should I be worried? Whether CVE-2025-64750 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
6. What actually determines whether CVE-2025-64750 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.
7. How do I fix CVE-2025-64750?
   • Upgrade github.com/sylabs/singularity/v4 to 4.3.5 or later
   • Upgrade github.com/sylabs/singularity/v4 to 4.1.11 or later