Executive brief
Anki, a popular flashcard and language learning application, contains a vulnerability in its internal media server. A malicious website visited by a user could send unauthorized commands to the Anki application running on the same computer. This could allow an attacker to read local files or trigger unintended actions within the software, potentially compromising user data or privacy.
Technical details
Anki versions prior to 25.09.3 launch a local HTTP server to serve media and interface components. The server fails to properly validate the 'Origin' and 'Host' headers, leading to an origin validation error (CWE-346). An attacker can exploit this by enticing a user to visit a malicious website, which then makes cross-origin requests to the local Anki server. The impact is highest on browsers like Firefox and Safari that lack robust Private Network Access (PNA) protections, potentially allowing the attacker to read local files or execute state-changing actions. The issue was addressed in version 25.09.3 by fixing a variable shadowing bug that interfered with host validation logic.
Affected products
- Ankitects Anki < 25.09.3
Timeline
- 2026-05-04: disclosed: Initial discovery/report by Tavis Ormandy
- 2026-05-07: patched: Version 25.09.3 released
- 2026-06-19: advisory: GitHub Security Advisory published
- 2026-07-07: advisory: CVE published to NVD