CVE-2019-7656 in Streaming Engine
Summary
by MITRE
A privilege escalation vulnerability in Wowza Streaming Engine 4.7.7 and 4.7.8 allows any unprivileged Linux user to escalate privileges to root. The installer sets too relaxed permissions on /usr/local/WowzaStreamingEngine/bin/* core program files. By injecting a payload into one of those files, it will run with the same privileges as the Wowza server, root. For example, /usr/local/WowzaStreamingEngine/bin/tune.sh could be replaced with a Trojan horse.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2019-7656 represents a critical privilege escalation flaw in Wowza Streaming Engine versions 4.7.7 and 4.7.8 affecting Linux systems. This vulnerability stems from inadequate permission settings on core executable files within the Wowza installation directory, specifically in the /usr/local/WowzaStreamingEngine/bin/ path. The flaw creates a dangerous attack surface where unprivileged users can manipulate critical system components to gain root-level access, fundamentally compromising system security and integrity.
The technical implementation of this vulnerability relies on the principle of least privilege violation, where the installer fails to properly secure critical executables that run with elevated privileges. When Wowza Streaming Engine is installed, it creates executable files in the bin directory with overly permissive permissions that allow any local user to modify or replace these binaries. This configuration directly violates security best practices and creates a persistent backdoor for attackers who can inject malicious payloads into these files. The attack vector specifically targets the tune.sh script and similar executables, which are executed with root privileges by the Wowza server process, making them ideal targets for privilege escalation attacks.
The operational impact of CVE-2019-7656 is severe and far-reaching, as it allows any local user to achieve complete system compromise without requiring any special privileges or advanced exploitation techniques. Once an attacker replaces one of the vulnerable executable files with a malicious payload, the injected code executes with root privileges every time the Wowza service runs, providing persistent access to the entire system. This vulnerability effectively nullifies the security model of the Linux system, as it bypasses traditional user permission controls and allows attackers to perform any action including but not limited to data exfiltration, system modification, privilege escalation to other users, and establishment of persistent backdoors. The vulnerability is particularly dangerous because it does not require network access or complex exploitation methods, making it easily exploitable in both internal and external attack scenarios.
Mitigation strategies for CVE-2019-7656 should focus on immediate permission hardening of the affected directories and files. System administrators must immediately verify and correct the file permissions on all executables within /usr/local/WowzaStreamingEngine/bin/ to ensure they are not writable by non-root users. The recommended approach involves setting restrictive permissions using chmod commands to prevent modification of critical executables. Additionally, implementing proper file integrity monitoring tools can help detect unauthorized changes to these critical system files. Organizations should also consider upgrading to patched versions of Wowza Streaming Engine where this vulnerability has been addressed, and implement comprehensive security auditing procedures to identify and remediate similar permission issues across the entire system infrastructure. This vulnerability aligns with CWE-276, which addresses improper file permissions, and represents a clear violation of the principle of least privilege as outlined in various cybersecurity frameworks including the MITRE ATT&CK framework's privilege escalation tactics.
The long-term security implications of this vulnerability extend beyond immediate exploitation, as it highlights the importance of proper software installation security practices and the need for comprehensive security reviews of third-party applications. System administrators should implement regular security assessments to identify similar permission issues in other software installations and establish robust security baseline configurations that prevent such vulnerabilities from being introduced during the software deployment process. The vulnerability also underscores the critical need for secure software development practices where installation scripts properly configure file permissions and implement proper access controls from the initial deployment phase.