xdg-dbus-proxy 0.1.9 fixes a security vulnerability, CVE-2026-94422: <https://github.com/flatpak/xdg-dbus-proxy/security/advisories/GHSA-2cgv-pwcq-wvpq> <https://github.com/flatpak/xdg-dbus-proxy/releases/tag/0.1.9>
All versions older than 0.1.9 are vulnerable.
An incorrect implementation of message filtering in xdg-dbus-proxy versions before 0.1.9 allows an attacker to bypass the intended message filtering on the D-Bus session bus by setting a reply serial number on non-reply messages. xdg-dbus-proxy was designed to be part of the sandbox boundary for Flatpak, but it is released as a separate project and is sometimes used by other app frameworks such as Firejail. Impact ====== A malicious or compromised Flatpak app could achieve arbitrary code execution outside its sandbox. If other app frameworks rely on xdg-dbus-proxy in the same way that Flatpak does, then they will have an equivalent vulnerability until xdg-dbus-proxy is updated. Patches ======= Fixed in 0.1.9 by commits: * e5702fc "proxy: Don't assume that only returns and errors have a reply-serial" * fc027f7 "proxy: Make it clearer which direction messages are going in" * e4465a0 "proxy: Only allow replies to go to the correct destination" Test coverage is provided by commits * 4427d5d "tests: Add basic test coverage for reply handling" * e7f2f89 "tests: Assert that "replies" of inappropriate types aren't accepted" * 78045ce "tests: Assert that forged replies cannot be sent to wrong destination" Workarounds =========== Avoid running untrusted Flatpak apps. Avoid running untrusted apps via other frameworks that use xdg-dbus-proxy. Credits ======= Reported by @refi64.
-- Simon McVittie, Collabora Ltd. / Debian
