CVE-2026-34078

Critical

Published: 07 April 2026

Published

07 April 2026

Modified

24 April 2026

KEV Added

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Patch

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CVSS Score 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Score 0.0006 17.1th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34078 is a critical-severity UNIX Symbolic Link (Symlink) Following (CWE-61) vulnerability in Flatpak Flatpak. Its CVSS base score is 10.0 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Escape to Host (T1611); ranked at the 17.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Escape to Host (T1611) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Directly addresses the CVE by requiring timely patching of vulnerable Flatpak versions prior to 1.16.4 to fix the symlink path traversal in sandbox-expose options.

RA-5 Vulnerability Monitoring and Scanning good match

detect

Enables identification of the vulnerable Flatpak installation through regular vulnerability scanning and monitoring of advisories such as GHSA-cc2q-qc34-jprg.

CM-11 User-installed Software partial match

prevent

Reduces exploitation likelihood by prohibiting or restricting user installation of malicious Flatpak applications that abuse the sandbox-expose symlink vulnerability.

MITRE ATT&CK Enterprise TechniquesAI

T1611 Escape to Host Privilege Escalation

Adversaries may break out of a container or virtualized environment to gain access to the underlying host.

attack.mitre.org →

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

Why these techniques?

Vulnerability enables sandbox escape via symlink-controlled host path mounting in Flatpak, directly mapping to T1611 (Escape to Host) and facilitating T1068 (Exploitation for Privilege Escalation) for host code execution.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Flatpak is a Linux application sandboxing and distribution framework. Prior to 1.16.4, the Flatpak portal accepts paths in the sandbox-expose options which can be app-controlled symlinks pointing at arbitrary paths. Flatpak run mounts the resolved host path in the sandbox.…

This gives apps access to all host files and can be used as a primitive to gain code execution in the host context. This vulnerability is fixed in 1.16.4.

Deeper analysisAI

CVE-2026-34078 is a critical vulnerability in Flatpak, a Linux application sandboxing and distribution framework, affecting versions prior to 1.16.4. The issue stems from the Flatpak portal accepting paths in the sandbox-expose options that can be controlled by applications as symbolic links pointing to arbitrary host paths. When Flatpak run processes these, it mounts the resolved host path inside the sandbox, bypassing intended isolation and exposing host files to the sandboxed application. This flaw, associated with CWE-61 (Symbolic Link Race Condition), carries a CVSS v3.1 base score of 10.0 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H).

The vulnerability can be exploited by remote attackers with no privileges or user interaction required, typically through a malicious Flatpak application distributed via untrusted sources. An attacker crafts an app-controlled symlink in the sandbox-expose options to target sensitive host paths, granting the sandboxed app read/write access to arbitrary host files upon execution via Flatpak run. This access serves as a primitive for achieving code execution in the host context, potentially leading to full system compromise on affected Linux systems using vulnerable Flatpak installations.

Advisories, including the Flatpak GitHub security advisory (GHSA-cc2q-qc34-jprg) and discussions on oss-security mailing lists, confirm the vulnerability is fixed in Flatpak 1.16.4. Security practitioners should prioritize upgrading to version 1.16.4 or later and review Flatpak configurations for exposed paths, particularly in environments distributing third-party Flatpak apps.