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GHSA-j3rw-fx6g-q46j
No affected components available
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.
The vulnerability requires local access to the device to be exploited. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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