CVE-2026-97029
Description
Flatpak's process ID namespace separation does not prevent a sandboxed app's kill(0, signal) or killpg(0, signal) calls from reaching processes outside the sandbox that share the same process group. A malicious or compromised Flatpak app can use this to cause denial of service by terminating processes outside its sandbox, such as the desktop shell.
Statement
Red Hat estimates the CVSSv3.1 vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H from the upstream CVSSv4.0 vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N (score 5.1).
Exploitation requires a victim to install and run a malicious or compromised Flatpak app (UI:R), after which the process-group signal leak is triggered automatically with no additional attacker privileges or access complexity beyond that of a normal sandboxed app (AV:N, AC:L, PR:L). No subsequent system beyond the local host is affected, so scope is unchanged (S:U). There is no confidentiality or integrity impact (C:N, I:N). The availability impact is scored for the reasonable worst case described in the upstream advisory: under common desktop configurations (e.g. GNOME Shell), a malicious app can terminate the desktop shell itself, ending the user's entire session (A:H).
Mitigation
Run Flatpak apps in a new session (setsid flatpak run ... or setsid() in the parent) or a new process group (setpgid (0, 0) in the parent), or avoid running untrusted Flatpak apps.
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 v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.7 | N/A | 5.7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
The exploitation of a weakness in low-privileged areas of the software can be leveraged to reach higher-privileged areas without having to overcome any additional obstacles.
Acknowledgements
Red Hat would like to thank Guthrie Armstrong (Coalition Inc.) for reporting this issue.
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