Google Chrome EUVD-2026-50913

Exploitation requires the attacker to have ALREADY compromised the renderer process - this is a sandbox-escape primitive, not an initial-access bug - plus user interaction to render a crafted PDF file (CVSS UI:R). The specific trigger is untrusted input processed by the Notifications component via a malicious PDF. Limiting factors: the mandatory prior renderer compromise, the requirement that the victim open/render the attacker's PDF, and applicability only to Chrome versions before 151.0.7922.72; SSVC records Exploitation: none and the bug is not automatable, so it is not usable for unauthenticated one-shot remote takeover despite the PR:N in the CVSS vector.

The signals conflict sharply and must be read together. The CVSS 3.1 base score of 9.6 (AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H) looks critical, but it does not reflect the description's explicit precondition that the attacker must have ALREADY compromised the renderer process - this is a second-stage sandbox-escape primitive, not a standalone remote takeover, so AC:L/PR:N materially overstates ease of exploitation. Corroborating this, Chromium itself rated the security severity Low, CISA SSVC records Exploitation: none and Automatable: no (though Technical Impact: total), and EPSS is only 0.16% (6th percentile). There is no KEV listing and no public exploit identified. Net: this is a chainable component of a full exploit rather than a directly weaponizable single bug - real-world priority is moderate for defenders who patch Chrome on the normal cycle, higher only for high-value targets facing sophisticated exploit chains.

An attacker first uses a separate renderer-level bug to gain code execution inside Chrome's sandboxed renderer, then lures the victim to open or render a crafted PDF that abuses the Notifications input-validation flaw to escape the sandbox into the browser process. No public exploit is identified at time of analysis, and the chain depends on user interaction (UI:R) plus a pre-existing renderer compromise, making it a targeted rather than opportunistic scenario.