CVE-2023-39929

What it actually does

Uncontrolled DLL/library search path in libva allows a local authenticated attacker to load a malicious shared object from a user-writable directory, resulting in arbitrary code execution with elevated privileges.

Why it matters to the business

Attackers with limited local access can obtain administrative rights on affected systems, enabling data theft, ransomware deployment, or persistence across endpoints that use the library for video processing.

How an attack unfolds

An attacker with a local account plants a malicious library in a directory that precedes the legitimate one in the search order, then invokes any application that loads libva; the malicious library is executed instead, granting privilege escalation without user interaction beyond the initial foothold.

How to fix it

Upgrade libva to version 2.20.0 or later on all affected systems; rebuild or reinstall dependent packages that statically link older versions; verify that runtime library search paths no longer include untrusted directories.

How to confirm the fix worked

Query installed package version of libva and confirm it is 2.20.0 or newer; run ldd or equivalent on binaries that depend on libva to ensure only signed or trusted libraries are resolved; perform a controlled test by placing a benign marker library in candidate search paths and confirming it is not loaded.

Typical attack path

1. Obtain limited local user account on target system
2. Identify writable directory appearing earlier in the uncontrolled search path
3. Place crafted malicious shared object matching expected library name
4. Trigger execution of any process that dynamically loads libva
5. Malicious code runs with higher privileges and establishes persistence or performs further actions

How to detect it

Review process creation and module load events for unexpected shared objects loaded from user-writable paths; correlate with libva usage by inspecting command lines or parent processes; examine audit logs for file writes matching common library naming patterns in search directories.

What your security team should do

• Immediately inventory all systems using libva and schedule upgrades to 2.20.0+
• Harden library search paths via environment variables or build-time flags to exclude user-writable locations
• Enable application whitelisting or mandatory code signing to block unsigned libraries
• Monitor for unexpected library loads from non-system directories using EDR telemetry