Ankitects Anki path traversal and origin bypass in local HTTP server

Executive brief

Anki, a popular flashcard learning application, uses a local web server to display content. A security flaw in this server allows malicious websites to bypass security boundaries and steal private files from your computer if they know the file's location. Users of Firefox and Safari are at higher risk because these browsers currently lack specific protections against websites talking to local applications.

Technical details

Anki's local HTTP server, implemented in the 'aqt' package, contains two primary flaws: insufficient validation of the 'Origin' HTTP header and path traversal vulnerabilities in certain endpoints (CWE-346, CWE-22). An attacker can exploit these by hosting a malicious website that makes cross-origin requests to the local Anki server (typically on localhost). If the attacker knows or guesses a local file path, they can exfiltrate the contents of that file. The impact is mitigated in Chromium-based browsers by Private Network Access (PNA) restrictions, but browsers like Firefox and Safari remain more susceptible. The issue is resolved in version 25.09.3.

Affected products

• Ankitects Anki <= 25.9.2
• Ankitects aqt <= 25.9.2

Timeline

• 2026-06-19: disclosed
• 2026-06-19: advisory
• 2026-06-19: patched: Fixed in version 25.09.3

References

• https://api.github.com/users/taviso
• https://github.com/taviso
• https://api.github.com/users/taviso/gists%7B/gist_id%7D
• https://api.github.com/users/taviso/repos
• https://avatars.githubusercontent.com/u/123814?v=4
• https://api.github.com/users/taviso/events%7B/privacy%7D