Description
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.
References8
- access.redhat.com/security/cve/CVE-2026-94422
- bugzilla.redhat.com/show_bug.cgi?id=2542235
- github.com/flatpak/xdg-dbus-proxy/commit/e4465a0dfe96da3b39929a…
- github.com/flatpak/xdg-dbus-proxy/commit/e5702fca4dba9600721921…
- github.com/flatpak/xdg-dbus-proxy/commit/fc027f759316fb2a6c4564…
- github.com/flatpak/xdg-dbus-proxy/security/advisories/GHSA-2cgv…
- www.openwall.com/lists/oss-security/2026/09/23/5
- lists.debian.org/debian-lts-announce/2026/10/msg00050.html
Metrics
- CVSS 3.1
-
8.8
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - CVSS 4.0
-
8.7
HIGH
Score source: CNA
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 43 · as of 10 November 2026
- CWE
- CWE-290
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.