CVE-2026-97027 in Red Hat
Summary
by MITRE • 09/29/2026
Flatpak passes through arbitrary vendor-extension keys unmodified when exporting an application's Desktop Entry (.desktop) and D-Bus Service (.service) files, instead of validating against an allowlist. A malicious Flatpak app can use this to cause denial of service (e.g. forced application restart loops) or to influence host D-Bus/systemd activation behavior beyond what the sandbox is intended to permit.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified in Flatpak represents a critical failure in input validation and access control mechanisms within the application runtime environment. Specifically, when exporting an application's Desktop Entry (.desktop) files or D-Bus Service (.service) definitions, the system fails to sanitize vendor-extension keys that are passed through from the sandboxed application context to the host operating system. Instead of enforcing a strict allowlist to validate these extension fields against known safe and expected parameters, Flatpak blindly propagates arbitrary key-value pairs. This architectural oversight allows any content included in these configuration files by an untrusted or maliciously constructed flatpak package to be directly interpreted by the host's desktop environment and service management subsystems without sufficient scrutiny.
From a technical perspective, this flaw stems from a lack of rigorous schema validation during the packaging and installation phases. Desktop Entry specifications allow for vendor-specific extensions using keys prefixed with X-, while D-Bus activation files define how services are launched on demand. By not restricting which extension keys can be exported to the host system, Flatpak inadvertently grants applications privileges that extend beyond their intended sandbox boundaries. A malicious actor crafting a flatpak application could embed specially crafted entries in these configuration files designed to exploit specific behaviors of common desktop environments or systemd instances running on the host machine.
The operational impact of this vulnerability is significant and multifaceted. The most immediate consequence is the potential for denial of service attacks against the user's session. By injecting malformed or excessively recursive activation commands into D-Bus service definitions, an attacker can trigger forced application restart loops that consume system resources such as CPU cycles and memory until the desktop environment becomes unresponsive or crashes entirely. Furthermore, this flaw enables unauthorized influence over host-level systemd activation behavior. An adversary could potentially register services or modify startup sequences in ways that bypass security policies, leading to privilege escalation scenarios where a sandboxed process gains control over critical system components outside its designated confinement zone.
This vulnerability aligns with CWE-20 Improper Input Validation and CWE-78 OS Command Injection principles, as it involves the processing of untrusted data without adequate sanitization before interacting with operating system services. In terms of threat modeling, this behavior corresponds to ATT&CK techniques related to Persistence via startup scripts or service registration (T1547) and potentially Defense Evasion by hiding malicious activities within legitimate configuration files. The ability to manipulate D-Bus activation mechanisms allows for persistent access that survives reboots and is difficult to detect through standard application-level monitoring tools because the activity appears as normal system service initialization.
Mitigation strategies must focus on implementing strict allowlisting at the Flatpak runtime level rather than relying on blacklist approaches or trusting input from untrusted sources. Developers should ensure that only predefined, safe vendor-extension keys are permitted during the export process for both Desktop Entry and D-Bus Service files. Additionally, sandboxing policies should be tightened to prevent applications from writing directly to host-level configuration directories unless explicitly authorized by the user with elevated privileges. Regular auditing of flatpak packages against updated security standards will help identify and remediate similar issues before they can be exploited in production environments.