Critical OpenCode Flaws Let Websites Hijack Your PC

OpenCode has two high‑severity flaws, CVE-2026-22813 and CVE-2026-22812, that researchers say could let attackers write malicious code onto a victim’s machine by visiting a webpage. The most critical, CVE-2026-22813, carries a CVSS score of 9.4 and exploits a Cross‑Site Scripting flaw to jump from the web UI to the local system.

According to the advisory, a malicious site can abuse the “server URL override feature” in the OpenCode web UI because HTML input is not sanitised, lacking DOMPurify or a CSP, enabling injection into the chat interface. Once executed, the script can call the local OpenCode API on localhost:4096 to spawn arbitrary processes, with JavaScript execution on http://localhost:4096 equating to code execution on the local machine.

CVE-2026-22812, with CVSS 8.8, reveals that the backend runs an unauthenticated HTTP server with permissive CORS, allowing any website to issue commands to visitors’ machines via a drive‑by attack; critical endpoints include POST /session/:id/shell and GET /file/content?path=: read arbitrary files. The flaws affect OpenCode versions prior to 1.0.216, and a patch in 1.0.216 (and likely later) has been released, with users urged to update immediately.