CVE-2026-39977
flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files
flatpak-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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Passive
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
7.1
flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files
flatpak-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.
- Record
CVE-2026-39977- CVSS 4.0
- 7.1 High
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 - Weakness
- CWE-22
- Updated
- 2026-11-02
EUVDEUVD-2026-21045
7.1
flatpak-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.
- Record
EUVD-2026-21045- CVSS 4.0
- 7.1 High
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 - Updated
- 2026-11-02
NVD
7.1
flatpak-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.
- Record
CVE-2026-39977- CVSS 4.0
- 7.1 High
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 - CVSS 3.1
- 6.3 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N - Weakness
- CWE-22
- Updated
- 2026-11-02
OSV
7.1
flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files
flatpak-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.
- Record
CVE-2026-39977- CVSS 4.0
- 7.1 High
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 - Weakness
- CWE-22
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-39977
6.3
flatpak-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.
- Record
DEBIAN-CVE-2026-39977- CVSS 3.1
- 6.3 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-39977
7.1
flatpak-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.
- Record
UBUNTU-CVE-2026-39977- CVSS 4.0
- 7.1 High
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 - CVSS 3.1
- 6.3 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:10590-1 No score
flatpak-builder-1.4.8-1.1 on GA media
These are all security issues fixed in the flatpak-builder-1.4.8-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:10590-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
flatpak-builderDebian:14 |
before 1.4.8-1, plus listed versions 1.4.4-21.4.5-11.4.6-11.4.6-21.4.7-1 |
1.4.8-1 |
flatpak-builderUbuntu:25.10 |
All versions, plus listed versions 1.4.4-21.4.4-2build11.4.5-11.4.6-2 |
None known |
flatpak-builderUbuntu:26.04:LTS |
before 1.4.8-1, plus listed versions 1.4.6-21.4.7-1 |
1.4.8-1 |
flatpak-builderopenSUSE:Tumbleweed |
before 1.4.8-1.1 | 1.4.8-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-39977 is a high vulnerability (CVSS 7.1) in Flatpak Flatpak-builder, published April 9, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 22nd percentile. Fixed in flatpak-builder 1.4.8-1.
References
github.com/flatpak/flatpak-builder/security/advisories/GHSA-6gm9-3g7m-3965
github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39977.json
nvd.nist.gov/vuln/detail/CVE-2026-39977
security-tracker.debian.org/tracker/CVE-2026-39977
ubuntu.com/security/CVE-2026-39977
cve.org/CVERecord?id=CVE-2026-39977
suse.com/security/cve/CVE-2026-39977