CVE-2026-34078: Flatpak has a complete sandbox escape leading to host file access and code execution in the host context

Severity: critical (CVSS 10.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-07 · updated 2026-07-24
Weakness: CWE-61

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.

Affected products

flatpak: through 1.16.3

References

https://github.com/flatpak/flatpak/security/advisories/GHSA-cc2q-qc34-jprg
http://www.openwall.com/lists/oss-security/2026/04/09/8
http://www.openwall.com/lists/oss-security/2026/04/10/14
https://access.redhat.com/errata/RHSA-2026:21755
https://access.redhat.com/errata/RHSA-2026:21756
https://access.redhat.com/errata/RHSA-2026:21757
https://access.redhat.com/errata/RHSA-2026:23417
https://access.redhat.com/errata/RHSA-2026:23418
https://access.redhat.com/errata/RHSA-2026:23419
https://access.redhat.com/errata/RHSA-2026:23420
https://access.redhat.com/errata/RHSA-2026:25068
https://access.redhat.com/errata/RHSA-2026:25381

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