# CVE-2026-90616

## Summary

- **CVE ID:** CVE-2026-90616
- **Severity:** HIGH
- **CVSS Score:** 7.4 (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** CWE-61
- **Published:** Sep 12, 2026
- **Last Modified:** Sep 14, 2026

## Description

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.

## Affected Products

- Flatpak — Flatpak (0)

## References

- [CNA](https://github.com/flatpak/flatpak/security/advisories/GHSA-8688-9x26-hhxj)
- [CNA](https://www.openwall.com/lists/oss-security/2026/08/11/9)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.17%
- **EPSS Percentile:** 6.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._