# CVE-2026-96807: Flatpak symlink attack on .ld.so with arbitrary file writes

Source: https://junglewise.ai/threats/cve-2026-96807-in-flatpak-before-1-18-1-a-malicious-sandboxed-app-can-replace  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-96807 · Severity: medium · CVSS 4 · Published 2026-09-23

Flatpak is a containerization technology that isolates applications in sandboxes. A malicious sandboxed application can exploit a symlink vulnerability to write files to arbitrary locations on the system outside its sandbox, potentially compromising system integrity. Although the filenames and file contents are fixed (not attacker-controlled), this could still be leveraged to disable services or degrade system functionality.

Vendors: [Freedesktop.Org](https://junglewise.ai/threats/vendors/freedesktop-org).

## Quick answers

**Is CVE-2026-96807 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96807 being exploited in the wild.

**How severe is CVE-2026-96807?** Medium severity, with a CVSS score of 4, published 23 September 2026.

**Which products and versions are affected?** Freedesktop.Org Flatpak before 1.18.1.

**Is there a fix for CVE-2026-96807?** A patch was published on 2026-08-11: Version 1.18.1 released with fixes; backports available for flatpak-1.16.x LTS branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-96807 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-96807?** Check whether you run Freedesktop.Org Flatpak at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A malicious sandboxed app can replace ~/.var/app/$appid/.ld.so with a symlink, causing the regenerate_ld_cache function to follow the symlink and write fixed-content files to arbitrary filesystem locations. This is a Time-of-Check-Time-of-Use (TOCTOU) / symlink attack that bypasses sandbox confinement. The attack requires the app to be running within the Flatpak sandbox to perform the symlink replacement before ld.so regeneration occurs.

## Affected products

- freedesktop.org Flatpak before 1.18.1

## Timeline

- 2026-08-11: disclosed
- 2026-08-11: patched: Version 1.18.1 released with fixes; backports available for flatpak-1.16.x LTS branch

## References

- [https://github.com/flatpak/flatpak/security/advisories/GHSA-99wv-m8rp-g58x](https://github.com/flatpak/flatpak/security/advisories/GHSA-99wv-m8rp-g58x)