Anki CVE-2026-59153

Exploitation requires three concurrent conditions: (1) the victim must have Anki open and its local HTTP server actively running at the time of the attack; (2) the victim must visit an attacker-controlled webpage in the same browser session; (3) the victim's browser must not enforce Private Network Access (PNA) protections - browsers such as recent Chromium releases with PNA enabled will block the cross-origin localhost request with a preflight rejection, defeating the attack. Authentication is not required from the attacker's perspective (PR:N), but the local server is implicitly 'authenticated' by being reachable only on the victim's own machine. The non-default condition limiting exploitation is the browser's PNA posture: Firefox and older Chromium builds without PNA represent the primary at-risk population.

The CVSS 4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N accurately reflects a low-priority finding. AT:P encodes the critical constraint: browsers with PNA enforcement already block this class of attack, meaning exploitation is limited to browsers lacking that protection. UI:A requires the victim to actively visit a malicious website while Anki is simultaneously running. The confidentiality, integrity, and availability impacts are all rated Low, and there is no subsequent-system impact. No EPSS data was provided, no CISA KEV listing exists, and no confirmed POC exploit code has been published - Tavis Ormandy's public tweet indicates researcher-level awareness but not weaponized exploitation. This is a genuine but low-urgency issue: the real-world attack surface is constrained by browser security evolution, and the impact even in a successful exploit is limited to minor data disclosure or localized state changes in the Anki process.

A victim with Anki running visits an attacker-controlled webpage. The page's JavaScript issues fetch requests targeting the Anki local HTTP server (typically on localhost with a fixed or discoverable port). In browsers without Private Network Access enforcement, these requests are forwarded without preflight, allowing the attacker to invoke Anki server endpoints that produce side effects such as reading media metadata or triggering local operations.