A security bypass vulnerability exists in Google Chrome AppBound cookie encryption mechanism due to insufficient validation of COM server paths during inter-process communication. A local low-privileged attacker can hijack the COM class identifier (CLSID) registration used by Chrome's elevation service and point it to a non-existent or malicious binary. When this hijack occurs, Chrome silently falls back to the legacy cookie encryption mechanism (protected only by user-DPAPI), thereby enabling cookie decryption by any user-context malware without SYSTEM-level access. This flaw bypasses the protections intended by the AppBound encryption design and allows cookie theft from Chromium-based browsers. Confirmed in Google Chrome with AppBound Encryption enabled. Other Chromium-based browsers may be affected if they implement similar COM-based encryption mechanisms.
During installation, installed file permissions are set to allow anyone to modify those files.
| Link | Tags |
|---|---|
| https://www.cyberark.com/resources/threat-research-blog/c4-bomb-blowing-up-chromes-appbound-cookie-encryption | technical description third party advisory |
| https://vulncheck.com/advisories/google-chrome-appbound-cookie-encryption | third party advisory |