Summary
A sandbox volume reference (volumeId, which may also be a volume name) was forwarded to the
runner and used to build the host bind-mount source path without confinement. A reference
containing path-traversal sequences could in principle resolve the mount source outside the
intended per-volume base directory.
Impact
Had the traversal been reachable, an authenticated user could have caused the runner to
bind-mount an unintended host path into their sandbox, with a worst-case impact of read and
write access to other tenants' volume data (per-volume FUSE mounts are world-readable and
writable).
Important: this path was not exploitable in any released version. A volume reference is
validated against the database before it reaches the runner, and the volume id column is a
UUID type, so a reference containing traversal sequences is rejected at validation time and
the request fails before any mount is constructed. We could not reproduce cross-tenant access
or an out-of-base host mount on a released build; the observable effect of the documented
payload was a server-side validation error. Severity is assessed as Medium on that basis.
Patches
Fixed in v0.186.0. Volume references are now resolved to the canonical volume UUID
server-side before reaching the runner, so a name can never flow downstream as a path
component, and the runner confines the mount source to the volume base directory and rejects
any non-UUID reference.
Workarounds
Upgrade to v0.186.0 or later. No configuration workaround is required for released versions,
which were not exploitable.
Credit
Reported by @vnth4nhnt from CyStack.
References
vnth4nhnt Reporter
Summary
A sandbox volume reference (
volumeId, which may also be a volume name) was forwarded to therunner and used to build the host bind-mount source path without confinement. A reference
containing path-traversal sequences could in principle resolve the mount source outside the
intended per-volume base directory.
Impact
Had the traversal been reachable, an authenticated user could have caused the runner to
bind-mount an unintended host path into their sandbox, with a worst-case impact of read and
write access to other tenants' volume data (per-volume FUSE mounts are world-readable and
writable).
Important: this path was not exploitable in any released version. A volume reference is
validated against the database before it reaches the runner, and the volume id column is a
UUID type, so a reference containing traversal sequences is rejected at validation time and
the request fails before any mount is constructed. We could not reproduce cross-tenant access
or an out-of-base host mount on a released build; the observable effect of the documented
payload was a server-side validation error. Severity is assessed as Medium on that basis.
Patches
Fixed in v0.186.0. Volume references are now resolved to the canonical volume UUID
server-side before reaching the runner, so a name can never flow downstream as a path
component, and the runner confines the mount source to the volume base directory and rejects
any non-UUID reference.
Workarounds
Upgrade to v0.186.0 or later. No configuration workaround is required for released versions,
which were not exploitable.
Credit
Reported by @vnth4nhnt from CyStack.
References