CVE-2015-7985 in Steam
Summary
by MITRE
Valve Steam 2.10.91.91 uses weak permissions (Users: read and write) for the Install folder, which allows local users to gain privileges via a Trojan horse steam.exe file.
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability identified as CVE-2015-7985 affects Valve Steam client version 2.10.91.91 and represents a critical privilege escalation issue stemming from improper file system permissions. This flaw allows local attackers to elevate their system privileges by exploiting weak access controls on the Steam installation directory. The vulnerability specifically manifests through the use of weak permissions that grant the Users group both read and write access to the installation folder, creating an exploitable attack surface for malicious actors.
The technical implementation of this vulnerability involves the manipulation of the Steam installation directory through a Trojan horse approach where an attacker places a malicious steam.exe file in the installation folder. This malicious executable can then be executed with elevated privileges due to the weak permissions structure. The vulnerability operates under the principle of privilege escalation by design, where a local user with standard account privileges can leverage the weak file system permissions to execute code with higher privileges than initially granted. This represents a classic case of insecure permissions that directly violates the principle of least privilege and creates a persistent backdoor for attackers.
From an operational impact perspective, this vulnerability enables local users to gain unauthorized access to elevated system privileges, potentially allowing them to install malicious software, modify system files, or access sensitive data. The attack vector is particularly concerning because it requires minimal sophistication to exploit, making it attractive to attackers who may not possess advanced technical skills. The vulnerability can be leveraged to establish persistent access to the system and potentially escalate further to obtain administrative privileges or access to network resources. This weakness in the Steam client's permission model creates a persistent threat vector that remains active until the installation directory permissions are properly configured.
The security implications of this vulnerability extend beyond the immediate privilege escalation, as it represents a fundamental flaw in the software's security architecture and access control implementation. The vulnerability aligns with CWE-276, which specifically addresses improper permissions and access control issues, and can be mapped to ATT&CK technique T1068, which covers local privilege escalation through the use of weak permissions. Effective mitigation requires immediate implementation of proper file system permissions where the installation directory is secured with restrictive access controls, ensuring that only authorized users or processes can modify the contents. Additionally, users should be advised to regularly audit their system permissions and implement proper security monitoring to detect unauthorized modifications to critical system directories. The vulnerability underscores the importance of maintaining secure default configurations and proper access control mechanisms in software installations to prevent exploitation by local attackers.