CVE-2026-107466 in Red Hat
Summary
by MITRE • 10/08/2026
A flaw was found in flatpak-builder. This vulnerability allows an attacker to cause information disclosure by convincing a user or continuous integration (CI) system to process a crafted build manifest. By specifying local file Uniform Resource Identifiers (URIs) within source download definitions, the builder bypasses directory confinement checks. As a result, sensitive host files accessible to the build process can be read and incorporated into the build artifacts.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability identified in flatpak-builder represents a significant security flaw related to improper input validation and insufficient access control mechanisms within the application packaging tool. Flatpak is widely used for distributing sandboxed desktop applications, relying on strict confinement policies to isolate processes from the host system. However, this specific weakness allows an attacker to circumvent these safeguards by exploiting how source URIs are processed during the build phase. The core issue lies in the builder's failure to adequately restrict or validate Uniform Resource Identifiers (URIs) specified within the build manifest files. When a user or an automated continuous integration system processes a maliciously crafted manifest, the tool does not enforce directory confinement checks for local file paths as rigorously as it does for remote resources. This oversight creates a pathway for unauthorized data exfiltration from the host environment into the constructed application artifacts.
From a technical perspective, the flaw stems from the handling of source definitions in the build configuration. By specifying local file URIs that point to sensitive areas of the filesystem accessible by the user running the build process or the CI service account, an attacker can instruct flatpak-builder to read and embed these files into the final package. This behavior bypasses the expected sandboxing boundaries because the builder operates with the privileges of the invoking entity but fails to apply additional restrictions when accessing local resources defined in manifests that are not strictly validated against a whitelist or confined directory structure. Consequently, any file readable by the build process can be included in the output, effectively turning the packaging tool into an instrument for data theft rather than just application distribution.
The operational impact of this vulnerability is severe, particularly in environments where flatpak-builder is used within continuous integration pipelines or shared development workspaces. In a CI context, if a malicious manifest is introduced through a compromised repository or social engineering attack, it can exfiltrate sensitive configuration files, credentials, source code secrets, or other proprietary data stored on the build server's filesystem. For individual developers, convincing a user to process a crafted manifest could lead to the leakage of personal documents or system configurations that were inadvertently made accessible during the build operation. The resulting artifacts may appear legitimate while silently carrying exfiltrated data, making detection difficult without deep inspection of the package contents and their construction history.
This vulnerability aligns with CWE-200, which classifies it as an Information Exposure Vulnerability, specifically involving exposure of sensitive information to unauthorized actors through improper access controls. It also relates to CWE-78, Improper Neutralization of Special Elements used in an OS Command, although the primary vector is file inclusion rather than command injection. In terms of the MITRE ATT&CK framework, this behavior corresponds to techniques under Data from Local System Retrieval and potentially Exfiltration Over Alternative Protocol if the artifacts are subsequently uploaded to a remote server controlled by the attacker. The attack pattern leverages trusted software components to bypass security boundaries, highlighting risks associated with supply chain integrity and manifest validation processes in build automation tools.
Mitigation strategies should focus on strict input validation and enhanced confinement policies within flatpak-builder itself. Developers and system administrators must ensure that manifests are sourced from trusted repositories and verified for integrity before processing. Upgrading to patched versions of flatpak-builder where this issue has been addressed is the primary remediation step, as these updates typically enforce stricter checks on local file URIs and prevent access outside designated source directories unless explicitly permitted through secure mechanisms. Additionally, CI systems should be configured with least-privilege principles, ensuring that build processes run in isolated environments with minimal filesystem access rights to reduce the potential impact of such manifest-based attacks. Regular auditing of build manifests for unexpected file references can also help detect malicious configurations before they are executed.