EUVD-2026-76911
GHSA-vhx5-8pfj-7wrv
Severity by source
AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
S:C upgraded from NVD S:U because the vulnerability is a sandbox escape that directly compromises the host system beyond the sandboxed component.
Primary rating from Vendor (mitre).
CVSS VectorVendor: mitre
Lifecycle Timeline
4DescriptionCVE.org
In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel, which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will become mounted inside the sandbox.
AnalysisAI
Sandbox escape in Flatpak before 1.18.1 allows a malicious sandboxed application to gain arbitrary read and write access to host filesystem paths, with direct escalation to code execution outside the sandbox. The root cause is missing symlink validation in Flatpak's app data directory bind-mount logic: attacker-controlled path components (such as the 'tmp' directory under ~/.var/app/APP_ID/cache/) can be replaced with symlinks pointing to arbitrary host locations, which the Linux kernel resolves when bwrap processes the bind-mount. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that a malicious Flatpak application be installed and executed by the target user - the attacker's code must be running inside a Flatpak sandbox on the target system. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 7.4 with vector AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H reflects a local attack of high complexity with full impact on confidentiality, integrity, and availability. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to Flatpak 1.18.1 or later, which introduces symlink protection for the attacker-controlled path components used during bind-mount construction. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all systems running Flatpak to identify affected versions via flatpak --version. …
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Same weakness CWE-61 – UNIX Symbolic Link (Symlink) Following
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External POC / Exploit Code
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