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CVE-2026-39977— flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files

Quick assessment

Affected
flatpak flatpak-builder
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

flatpak-builder是Flatpak开源的一个Flatpak应用构建工具。 flatpak-builder 1.4.5至1.4.8之前版本存在路径遍历漏洞，该漏洞源于license-files清单键的路径解析和验证不足，可能导致从主机读取任意文件并捕获到构建输出中。

AI Predicted 8.8 Difficulty: Easy EPSS 0.38% · P30

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery
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I. Basic Information for CVE-2026-39977

Vulnerability Information
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Vulnerability Title
flatpak-builder has a path traversal leading to arbitrary file read on host when installing licence files
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
flatpak-builder 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
flatpak-builder是Flatpak开源的一个Flatpak应用构建工具。 flatpak-builder 1.4.5至1.4.8之前版本存在路径遍历漏洞，该漏洞源于license-files清单键的路径解析和验证不足，可能导致从主机读取任意文件并捕获到构建输出中。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
flatpak flatpak-builder >= 1.4.5, < 1.4.8 -

II. Public POCs for CVE-2026-39977

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III. Intelligence Information for CVE-2026-39977

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Vendor Advisories for CVE-2026-39977 (1)

IV. Related Vulnerabilities

Same vendor: flatpak
Same weakness: CWE-22

V. Comments for CVE-2026-39977

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