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Fencer Vulns
critical 9.9

CVE-2026-120308 json

Beta9 host filesystem exposure via volume path traversal

published 2026-11-01 7 d ago modified 2026-11-02 6 d ago also EUVD-2026-114842

cvss
9.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

A Beta9 tenant can attach a volume when deploying a function, endpoint, or task queue. The gateway builds the host path by joining the shared volumes root, the workspace name, and the volume identifier from the stub configuration. Nothing checks that the identifier names a volume that workspace owns. Parent-directory segments in the identifier collapse the joined path to the worker's filesystem root, and the worker bind-mounts that path into the sandbox read-write unless the volume was explicitly marked read-only. A tenant with a workspace token can therefore read and write the worker's files, including other tenants' volumes stored on that machine. Confirmed against gateway 0.1.769 and worker 0.1.745. Fixed in gateway 0.1.776 and worker 0.1.756: volume identifiers and mount paths are validated before a mount is built, including for stubs saved before the check existed, and the gateway rejects a volume that does not exist or is not owned by the workspace.

Patch / fix

  • beam-cloud Beta9 gateway 0.1.776
  • beam-cloud Beta9 worker 0.1.756

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
6 d ago

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

  • beam-cloud Beta9 gateway
  • beam-cloud Beta9 worker

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
  • CWE-668 Exposure of Resource to Wrong Sphere

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.