CVE-2021-25630 in Collabora Online
Summary
by MITRE • 02/23/2021
"loolforkit" is a privileged program that is supposed to be run by a special, non-privileged "lool" user. Before doing anything else "loolforkit" checks, if it was invoked by the "lool" user, and refuses to run with privileges, if it's not the case. In the vulnerable version of "loolforkit" this check was wrong, so a normal user could start "loolforkit" and eventually get local root privileges.
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Analysis
by VulDB Data Team • 03/04/2021
The vulnerability identified as CVE-2021-25630 represents a critical privilege escalation flaw within the loolforkit program, which operates as a privileged component designed to execute under the control of a dedicated non-privileged user account named "lool". This security mechanism was intended to establish a clear separation between privileged operations and regular user access, creating a controlled environment where only authorized processes could elevate privileges. The system architecture relied on proper user validation checks to ensure that loolforkit could only be invoked by the designated lool user, thereby preventing unauthorized privilege escalation. However, the implementation contained a fundamental flaw that undermined this security model.
The technical flaw in loolforkit stems from an incorrect implementation of user authentication checks during program initialization. Specifically, the validation logic failed to properly verify the invoking user's identity, allowing any local user to bypass the intended security controls. This error likely involved improper handling of user ID comparisons or environment variable manipulation that could be exploited by an attacker to masquerade as the legitimate lool user. The vulnerability manifests as a failure in access control enforcement, where the program's privilege escalation mechanism operates without proper verification of the caller's credentials. This represents a classic case of inadequate input validation and privilege checking, which can be classified under CWE-284 Access Control Issues.
The operational impact of this vulnerability is severe and directly enables local privilege escalation from regular user level to root privileges. An attacker with local access to the system can simply invoke loolforkit as a normal user, bypassing the intended security controls, and subsequently execute privileged operations that would otherwise be restricted. This creates a significant risk for any system where loolforkit is deployed, as it essentially removes the security boundary between regular users and system administrators. The vulnerability undermines the principle of least privilege, allowing unauthorized users to gain full system control, potentially leading to data compromise, system takeover, and persistence mechanisms. This type of vulnerability is particularly dangerous in multi-user environments or systems where regular users have access to command line interfaces.
Mitigation strategies for CVE-2021-25630 should focus on immediate patching of the loolforkit program to correct the user validation logic and restore proper privilege checking mechanisms. Organizations should implement comprehensive access control reviews to ensure that all privileged programs properly validate user identities before executing elevated operations. The fix must address the root cause by implementing robust user authentication checks using proper system APIs and ensuring that environment variables cannot be manipulated to bypass validation. Additionally, system administrators should conduct thorough audits of similar privilege escalation mechanisms within their environments, as this vulnerability pattern may exist in other programs with similar security models. This remediation aligns with ATT&CK technique T1068 Privilege Escalation through the exploitation of insecure program execution paths and improper access control validation. The vulnerability demonstrates the critical importance of proper privilege separation and access control implementation in preventing unauthorized system compromise.