CVE-2016-20090: Comodo Dragon Browser Privilege Escalation via Unquoted Service Path

Technical summary

The vulnerability stems from an unquoted service path vulnerability (CWE-428) in the DragonUpdater component of Comodo Dragon Browser. When Windows services use unquoted executable paths without proper access controls, an attacker can exploit a directory traversal or path resolution logic to inject a malicious binary. Since DragonUpdater operates with SYSTEM privileges, a successfully injected executable inherits those privileges. The service path itself is not explicitly quoted, meaning if the path contains spaces or ambiguous separators, Windows may attempt to execute an attacker-controlled binary first. A local user can prepare a malicious executable in a predictable location within the service search path and wait for the next service restart to achieve code execution with elevated privileges.

Business impact

Compromise of a machine running Comodo Dragon Browser with this vulnerability allows an attacker to escalate from user-level access to SYSTEM-level control. This enables wholesale system takeover, including installation of malware, theft of sensitive data, lateral movement to other systems on the network, and persistent backdoor installation. Organizations with Comodo Dragon Browser deployed, particularly in environments where non-administrative users have local access, face risk of insider or low-privilege attacker exploitation. The browser market share of Comodo Dragon is relatively small, but affected organizations should treat this as a critical local privilege escalation vector.

Affected systems

Comodo Dragon Browser versions up to and including 52.15.25.663 are affected. The vulnerability exists in the DragonUpdater service component, which is likely installed automatically with the browser. Any system with a vulnerable version of Comodo Dragon Browser is at risk if it permits local user access or if an attacker has already obtained low-privilege shell access via another vector. Organizations should identify all systems running Comodo Dragon Browser and determine their current version.

Exploitability

Exploitation requires local code execution capability—an attacker must either have a valid local user account on the system or have already compromised one via another vulnerability or social engineering. The attack does not require user interaction; once the attacker places a malicious executable in the service path, they simply wait for a service restart or system reboot, which will automatically execute their payload with SYSTEM privileges. Availability of unquoted service path exploitation tools in the security community makes this relatively straightforward to weaponize for anyone with local access. This is not an issue an attacker can trigger remotely or without administrative access, but the barrier to exploitation for a local attacker is low.

Remediation

Update Comodo Dragon Browser to a patched version released after 52.15.25.663. Verify the exact patched version from official Comodo documentation or the vendor advisory, as version numbers may vary by release channel. Additionally, apply immediate mitigating controls: restrict local user account creation and privileges on systems running vulnerable versions; monitor service restart activities and process creation logs for unusual patterns; and consider removing Comodo Dragon Browser if it is not a critical business requirement, replacing it with a fully patched alternative browser.

Patch guidance

Patch availability should be verified against Comodo's official security advisories and release notes. Users should update through the browser's built-in update mechanism or download the latest installer from Comodo's official website. After patching, verify that the DragonUpdater service path is now properly quoted and that SYSTEM privileges are still strictly necessary for the service's operation. Test in a non-production environment first to ensure compatibility with your deployment. If you cannot patch immediately, apply compensating controls such as tightening file system permissions on the service directory, disabling the DragonUpdater service if not required, or isolating affected systems from untrusted users.

Detection guidance

Monitor for creation of executables in predictable locations within the system PATH or service-related directories, particularly those that precede the legitimate DragonUpdater binary. Watch for unexpected service restarts or system reboots initiated by unprivileged users. Audit file system access to the DragonUpdater installation directory, particularly write access by non-administrative accounts. Review Windows Event Log for Service Control Manager events indicating service start failures followed by restarts, which may indicate exploitation attempts. Endpoint detection and response (EDR) tools should flag privilege escalation events following service restarts. Hash or sign the legitimate DragonUpdater executable so that any substitution can be detected.

Why prioritize this

This vulnerability merits HIGH priority because it enables local privilege escalation to SYSTEM level with minimal complexity once access is obtained. The CVSS score of 7.8 reflects the high impact (full system compromise) and low attack complexity. Although it requires prior local access, organizations should treat this as a critical control point in their local privilege escalation defenses. Prioritize patching any systems where Comodo Dragon Browser is used by multiple users or where local access is difficult to control.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) is derived from attack vector Local, low attack complexity, low privileges required, no user interaction needed, and high impact across confidentiality, integrity, and availability. The local-only attack vector prevents a remote score, but the certainty and severity of code execution as SYSTEM justifies the HIGH classification. Organizations relying on local security boundaries should weight this risk higher in their remediation planning.

Frequently asked questions