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CVE-2026-39977

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

7.1 HighFix available

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

0.30%Up 0.3 points since Apr 10, 2026
90%50%10%1%

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 HighCVSS: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 HighCVSS: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 HighCVSS: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 MediumCVSS: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 HighCVSS: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 MediumCVSS: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 HighCVSS: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 MediumCVSS: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

Affected packages
PackageAffectedFixed
flatpak-builder
Debian: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-builder
Ubuntu:25.10
All versions, plus listed versions
1.4.4-21.4.4-2build11.4.5-11.4.6-2
None known
flatpak-builder
Ubuntu:26.04:LTS
before 1.4.8-1, plus listed versions
1.4.6-21.4.7-1
1.4.8-1
flatpak-builder
openSUSE:Tumbleweed
before 1.4.8-1.1
1.4.8-1.1

History

History
RecordedChangedSources
first indexedCVE 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

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