Impact

In Apptainer versions less than 1.4.5, a container can disable two of the forms of the little used --security option, in particular the forms --security=apparmor:<profile> and --security=selinux:<label> which otherwise put restrictions on operations that containers can do. The --security option has always been mentioned in Apptainer documentation as being a feature for the root user, although these forms do also work for unprivileged users on systems where the corresponding feature is enabled. Apparmor is enabled by default on Debian-based distributions and SElinux is enabled by default on RHEL-based distributions, but on SUSE it depends on the distribution version.

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

Patches

Ineffective write of selinux process labels is addressed via an update to the containers/selinux dependency in https://github.com/apptainer/apptainer/pull/3226. That update brings in the upstream fix for https://github.com/advisories/GHSA-cgrx-mc8f-2prm which was for a different but related vulnerability.

Ineffective write of apparmor process profiles is addressed in commit 4313b42.

Failure to detect apparmor / selinux support, when --security flags are provided, is made an error rather than a warning in commit 82f1790.

Workarounds

There are no known workarounds, other than to define system-wide apparmor / selinux policy for Apptainer itself. This would apply to all containers, not just those run with the --security flags, and could impact the operation of Apptainer itself.

References

Thanks to Sylabs for finding this issue, fixing it in https://github.com/sylabs/singularity/security/advisories/GHSA-wwrx-w7c9-rf87 which was easy to import into Apptainer, and disclosing it early to the Apptainer project for a coordinated release.

The related upstream runc disclosure which inspired the investigation is https://github.com/opencontainers/runc/security/advisories/GHSA-cgrx-mc8f-2prm.

• https://github.com/apptainer/apptainer/security/advisories/GHSA-j3rw-fx6g-q46j
• https://github.com/opencontainers/runc/security/advisories/GHSA-cgrx-mc8f-2prm
• https://github.com/sylabs/singularity/security/advisories/GHSA-wwrx-w7c9-rf87
• https://nvd.nist.gov/vuln/detail/CVE-2025-65105
• https://github.com/apptainer/apptainer/pull/3226
• https://github.com/apptainer/apptainer/commit/4313b42717e18a4add7dd7503528bc15af905981
• https://github.com/apptainer/apptainer/commit/82f17900a0c31bc769bf9b4612d271c7068d8bf2
• https://github.com/advisories/GHSA-j3rw-fx6g-q46j