CVE-2026-120307: The Beta9 worker serves the sandbox file API from outside the container
Affects beta9Source GCVE Database
Not known to be exploited · CVSS 9.9 Critical : upgrade to 0.1.756 as a priority.
Data as of 1 Nov 2026, 16:30 UTC
Thin evidence
One scorer or none| CNA (JFROG) | CVSS 3.1 | 9.9 |
|---|
- Patch
- Available – fixed in 0.1.756
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade beam-cloud/beta9 to 0.1.756.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
GitHubbeam-cloud/beta9pkg:github/beam-cloud/beta9Other threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available in Beta9 worker version 0.1.756. Users should upgrade to this version or later to ensure sandbox file operations and workspace sync use os.OpenRoot, which confines file access within container roots or mount sources, preventing directory traversal and symlink escape. No other mitigation is indicated or necessary once patched.
Description
CVE-2026-120307 is a critical vulnerability in the Beta9 worker where the sandbox file API is improperly served from outside the container. This flaw allows a tenant with a workspace token and a running sandbox to access and manipulate files on the hosting worker as root, including files belonging to other tenants. The vulnerability arises from path resolution issues that allow directory traversal and symbolic link exploitation, enabling unauthorized file operations on the worker host. The issue is fixed in worker version 0.1.756 by restricting file operations to stay within the container root or mount source.
References
- nvd.nist.gov/vuln/detail/CVE-2026-120307 (opens in a new tab)
- github.com/beam-cloud/beta9/pull/1897 (opens in a new tab)
- github.com/beam-cloud/beta9/commit/a28bf12cf0007c792a25d8ed282b4e8bf6f30393 (opens in a new tab)
- github.com/beam-cloud/beta9 (opens in a new tab)
- github.com/beam-cloud/beta9/releases/tag/worker-0.1.756 (opens in a new tab)