xdg-dbus-proxy: message filtering bypass via reply serial allows sandbox escape
18Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.7
exploitation probability
—
observed exploitation
nono source reports it
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. A malicious or compromised Flatpak app could use this to achieve arbitrary code execution outside its sandbox. 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.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected products
xdg-dbus-proxyFedora · FedoraRed Hat · Red Hat Enterprise Linux 10Red Hat · Red Hat Enterprise Linux 9References
https://access.redhat.com/security/cve/CVE-2026-94422https://bugzilla.redhat.com/show_bug.cgi?id=2542235https://github.com/flatpak/xdg-dbus-proxy/commit/e4465a0dfe96da3b39929a30a1ac3a22b16223e3https://github.com/flatpak/xdg-dbus-proxy/commit/e5702fca4dba9600721921fbca2dbc39dc5ca400https://github.com/flatpak/xdg-dbus-proxy/commit/fc027f759316fb2a6c45648200b6f100202eb84ehttps://github.com/flatpak/xdg-dbus-proxy/security/advisories/GHSA-2cgv-pwcq-wvpqhttp://www.openwall.com/lists/oss-security/2026/09/23/5