CVE-2026-94422
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.
Statement
Red Hat's CVSSv3.1 score has been calculated from the upstream-provided CVSSv4 vector (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). The resulting CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H vector reflects a network-exploitable flaw with low attack complexity and no privileges required, but requiring a user (via a malicious/compromised Flatpak app) to interact with the D-Bus session bus. The proxy's failure to validate reply-serial numbers on non-reply messages allows a sandboxed app to bypass its message filter and reach otherwise-blocked D-Bus interfaces, resulting in a full loss of confidentiality, integrity, and availability of the host system outside the sandbox.
Mitigation
Avoid running untrusted Flatpak apps and avoid running untrusted apps via other frameworks that use xdg-dbus-proxy.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v4 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.7 | N/A | 8.7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Attack Requirements | None | N/A | None |
| Privileges Required | None | N/A | None |
| User Interaction | Passive | N/A | Passive |
| Vulnerable System Confidentiality | High | N/A | High |
| Vulnerable System Integrity | High | N/A | High |
| Vulnerable System Availability | High | N/A | High |
| Subsequent System Confidentiality | None | N/A | None |
| Subsequent System Integrity | None | N/A | None |
| Subsequent System Availability | None | N/A | None |
Vector
Red Hat: 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
cve.org: 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
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | 8.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
Estimated from upstream CVSS v4 vector (AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N): AT:N folded into AC:L, UI:P mapped to UI:R (v3.1 has no passive/active distinction), Scope Unchanged since SC/SI/SA are all None.
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
This weakness can allow an attacker to access resources which are not otherwise accessible without proper authentication.
Acknowledgements
Upstream acknowledges refi64 as the original reporter.
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