A race condition in Epiphany allows a malicious website to bypass the TLS/SSL certificate warning…

Why it is Yellow

• CVSS 6.8 medium

References

• https://access.redhat.com/security/cve/CVE-2026-115683
• https://beford.net/poc/ssl_poc.html
• https://bugzilla.redhat.com/show_bug.cgi?id=2560012
• https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/2245
• https://gitlab.gnome.org/GNOME/epiphany/-/work_items/2978
• https://gitlab.gnome.org/GNOME/epiphany/-/work_items/2978

Original description

A race condition in Epiphany allows a malicious website to bypass the TLS/SSL certificate warning page. Epiphany registers the main-world script message handler "tlsErrorPage" so its internal TLS error page can implement "Accept Risk and Proceed". The handler was registered immediately before loading the error page, leaving a brief window where the previously loaded untrusted origin could still call window.webkit.messageHandlers.tlsErrorPage.postMessage(...). The only authorization check compares a numeric WebKit page id that increments predictably; an attacker can burst-guess ids and approve a certificate exception with no user click. If a victim visits malicious site A that redirects to site B with an invalid certificate, site A can, for a few milliseconds, disable TLS certificate error warnings for host B until Epiphany is restarted, enabling man-in-the-middle or site spoofing for that host. Upstream report: https://gitlab.gnome.org/GNOME/epiphany/-/work_items/2978 Proof of concept: https://beford.net/poc/ssl_poc.html Fix: https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/2245 (register handlers on LOAD_COMMITTED). No fixed release tagged yet; reporter and maintainer describe all current versions as affected. Maintainer notes the risky registration timing dates to commit 1da1caed (Epiphany 45.x era); before that the handlers were always registered and similarly reachable from web content.