CVE-2026-79617 in Pardus LightDM Greeter
Summary
by MITRE • 09/09/2026
Incorrect Permission Assignment for Critical Resource vulnerability in TÜBİTAK BİLGEM Software Technologies Research Institute Pardus LightDM Greeter allows Exploiting Incorrectly Configured Access Control Security Levels.
This issue affects Pardus LightDM Greeter: before 0.4.15.
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Analysis
by VulDB Data Team • 09/09/2026
The identified vulnerability in the TÜBİTAK BİLGEM Software Technologies Research Institute's Pardus distribution, specifically within the LightDM greeter component prior to version 0.4.15, represents a critical failure in access control mechanisms that governs authentication interfaces. This flaw is categorized under CWE-276, which denotes Incorrect Default Permissions for Critical Resource, and aligns with MITRE ATT&CK technique T1098, specifically the aspect of Account Manipulation involving SSH Authorized Keys or local account modifications if such pathways are exposed through the greeter interface. The LightDM greeter serves as the graphical login screen that authenticates users before granting access to the desktop environment. When this component is configured with overly permissive file system permissions or lacks proper validation of user input during session initialization, it creates an attack surface where unauthorized entities can manipulate authentication states or escalate privileges by exploiting these misconfigured security levels.
The technical nature of this vulnerability stems from a deviation in how the greeter application handles resource allocation and permission checks for critical configuration files or runtime data structures. In many Linux display manager implementations, certain temporary files, session cookies, or configuration overrides are created with default permissions that may allow read-write access to users other than root or the intended service account. If an attacker gains local shell access, even at a low-privilege level, they can potentially modify these resources to bypass authentication checks, inject malicious scripts into the login process, or alter session parameters to achieve unauthorized persistence. This is particularly dangerous in multi-user environments where shared systems are common, as it allows lateral movement from a standard user account toward administrative control without requiring valid credentials for higher-privilege accounts.
The operational impact of this vulnerability extends beyond simple privilege escalation; it compromises the integrity of the authentication subsystem itself. An attacker leveraging this flaw could establish persistent access by modifying greeter configurations to auto-login specific users, thereby bypassing password prompts entirely. Alternatively, they might intercept or alter session tokens if such mechanisms are utilized for single sign-on scenarios within the Pardus ecosystem. This undermines the fundamental security principle that the login interface must be a trusted boundary between untrusted user input and privileged system operations. The lack of strict permission enforcement means that the confidentiality and integrity guarantees provided by the operating system's mandatory access controls or standard Unix permissions are effectively nullified for these specific critical resources, leading to potential full system compromise if combined with other local exploits.
Mitigation strategies must focus on immediate remediation through software updates and rigorous configuration hardening. The primary defense is upgrading the LightDM greeter package to version 0.4.15 or later, where the developers have addressed these permission assignments by enforcing stricter file ownership and mode settings for all critical resources managed during the authentication process. Administrators should also audit system configurations using tools like find with specific permissions flags to identify any files related to display managers that are world-writable or group-readable when they should be restricted to root-only access. Implementing mandatory access control policies, such as SELinux or AppArmor profiles tailored for LightDM, can provide an additional layer of defense by restricting the greeter's ability to write to unauthorized paths regardless of file system permissions. Regular security audits and adherence to CIS benchmarks for Linux distributions will help ensure that such misconfigurations are detected and corrected before they can be exploited in production environments.