Singularity (an open source container platform) from version 3.1.1 through 3.6.3 has a vulnerability. Due to insecure handling of path traversal and the lack of path sanitization within `unsquashfs`, it is possible to overwrite/create any files on the host filesystem during the extraction with a crafted squashfs filesystem. The extraction occurs automatically for unprivileged (either installation or with `allow setuid = no`) run of Singularity when a user attempt to run an image which is a local SIF image or a single file containing a squashfs filesystem and is coming from remote sources `library://` or `shub://`. Image build is also impacted in a more serious way as it can be used by a root user, allowing an attacker to overwrite/create files leading to a system compromise, so far bootstrap methods `library`, `shub` and `localimage` are triggering the squashfs extraction. This issue is addressed in Singularity 3.6.4. All users are advised to upgrade to 3.6.4 especially if they use Singularity mainly for building image as root user. There is no solid workaround except to temporary avoid to use unprivileged mode with single file images in favor of sandbox images instead. Regarding image build, temporary avoid to build from `library` and `shub` sources and as much as possible use `--fakeroot` or a VM for that.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
| Link | Tags |
|---|---|
| https://github.com/hpcng/singularity/security/advisories/GHSA-7gcp-w6ww-2xv9 | third party advisory |
| https://github.com/hpcng/singularity/blob/v3.6.4/CHANGELOG.md#security-related-fixes | third party advisory release notes |
| https://github.com/hpcng/singularity/pull/5611 | third party advisory patch |
| https://github.com/hpcng/singularity/commit/eba3dea260b117198fdb6faf41f2482ab2f8d53e | third party advisory patch |
| http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00071.html | mailing list broken link third party advisory vendor advisory |
| http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00070.html | mailing list broken link third party advisory vendor advisory |
| http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00009.html | mailing list broken link third party advisory vendor advisory |