Junglewise Threat Intelligence

CVE-2026-34078: Flatpak sandbox escape via symlink following in sandbox-expose

CVE-2026-34078 · Severity: critical · CVSS 10 · Published 2026-04-07

Executive brief

Flatpak is a popular system used to run Linux applications in a secure, isolated environment (a sandbox). A critical vulnerability allows a malicious application to break out of this isolation by using specially crafted links to access any file on the host computer. This could allow an attacker to steal sensitive data or take full control of the user's system.

Technical details

A symlink following vulnerability (CWE-61) exists in the Flatpak portal's 'sandbox-expose' options. The portal fails to properly validate paths, allowing a sandboxed application to provide symlinks that point to arbitrary locations on the host filesystem. When Flatpak resolves these links and mounts the resulting paths into the sandbox, the application gains full read/write access to host files. This primitive can be leveraged to achieve arbitrary code execution in the host context, representing a complete sandbox escape. The issue is resolved in Flatpak version 1.16.4.

Affected products

  • Flatpak Flatpak < 1.16.4
  • Red Hat Enterprise Linux AppStream 8, 9, 10

Timeline

  • 2026-04-07: disclosed
  • 2026-04-07: advisory: GitHub Advisory GHSA-cc2q-qc34-jprg published
  • 2026-04-07: patched: Fixed in version 1.16.4

References

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