title: flatpak-builder can access files outside the build directory.
description: Flatpak is a Linux application sandboxing and distribution framework. A path traversal vulnerability affects versions of Flatpak prior to 1.12.3 and 1.10.6. flatpak-builder applies `finish-args` last in the build. At this point the build directory will have the full access that is specified in the manifest, so running `flatpak build` against it will gain those permissions. Normally this will not be done, so this is not problem. However, if `--mirror-screenshots-url` is specified, then flatpak-builder will launch `flatpak build --nofilesystem=host appstream-utils mirror-screenshots` after finalization, which can lead to issues even with the `--nofilesystem=host` protection. In normal use, the only issue is that these empty directories can be created wherever the user has write permissions. However, a malicious application could replace the `appstream-util` binary and potentially do something more hostile. This has been resolved in Flatpak 1.12.3 and 1.10.6 by changing the behaviour of `--nofilesystem=home` and `--nofilesystem=host`.
problem types: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
affected:
{
vendor: flatpak
product: flatpak
versions:
version: >= 1.11.0, < 1.12.3, status: affected
version: < 1.10.6, status: affected
}
metrics:
cvssV3_1: [
version: 3.1
vectorString: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
attackVector: NETWORK
attackComplexity: LOW
privilegesRequired: LOW
userInteraction: NONE
scope: CHANGED
confidentialityImpact: NONE
integrityImpact: HIGH
availabilityImpact: NONE
baseScore: 7.7
baseSeverity: HIGH
]