flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files

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Summary

CVECVE-2026-39977
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-09 20:16:26 UTC
Updated2026-04-09 20:16:26 UTC
Descriptionflatpak-builder is a tool to build flatpaks from source. From 1.4.5 to before 1.4.8, the license-files manifest key takes an array of paths to user defined licence files relative to the source directory of the module. The paths from that array are resolved using g_file_resolve_relative_path() and validated to stay inside the source directory using two checks - g_file_get_relative_path() which does not resolve symlinks and g_file_query_file_type() with G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS which only applies to the final path component. The copy operation runs on host. This can be exploited by using a crafted manifest and/or source to read arbitrary files from the host and capture them into the build output. This vulnerability is fixed in 1.4.8.

Risk And Classification

Primary CVSS: v4.0 7.1 HIGH from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.000460000 probability, percentile 0.143510000 (date 2026-04-10)

Problem Types: CWE-22 | CWE-22 CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.1HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED7.1HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
High
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Flatpak Flatpak-builder affected >= 1.4.5, < 1.4.8 Not specified

References

ReferenceSourceLinkTags
github.com/flatpak/flatpak-builder/security/advisories/GHSA-6gm9-3g7m-3965 [email protected] github.com
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