# CVE-2026-76925: Flatpak TOCTOU race condition in SystemHelper

Source: https://junglewise.ai/threats/cve-2026-76925-flatpak-toctou-race-condition-in-systemhelper  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-04. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-76925 · Severity: medium · CVSS 5.8 · Published 2026-09-04

Flatpak is a containerization system used to isolate and distribute desktop applications. A timing vulnerability in Flatpak's privileged installation process allows a local attacker to redirect files to arbitrary locations on the system, potentially exposing sensitive data or modifying critical application files before validation occurs.

Technologies: [Flatpak](https://junglewise.ai/threats/technologies/flatpak). Vendors: [Flatpak](https://junglewise.ai/threats/vendors/flatpak).

## Quick answers

**Is CVE-2026-76925 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76925 being exploited in the wild.

**How severe is CVE-2026-76925?** Medium severity, with a CVSS score of 5.8, published 4 September 2026.

**Which products and versions are affected?** Flatpak Flatpak.

**Is there a fix for CVE-2026-76925?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-76925 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-76925?** Check whether you run Flatpak. 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 Time-of-check to time-of-use (TOCTOU) race condition exists in the org.freedesktop.Flatpak.SystemHelper component, specifically in the Deploy() function. The vulnerability occurs because a privileged chmod operation executes before OSTree repository validation, creating a timing window where an attacker can manipulate symlinks to redirect to arbitrary files. An attacker with local access and low privileges can exploit this race condition during application deployment to achieve unauthorized file read/write access. The attack requires precise timing and does not need user interaction. A patch is expected from the Flatpak project.

## Affected products

- Flatpak Flatpak

## Timeline

- 2026-09-04: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-76925](https://access.redhat.com/security/cve/CVE-2026-76925)

## Related threats

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- [Flatpak process ID namespace isolation bypass](https://junglewise.ai/threats/cve-2026-97029-flatpak-s-process-id-namespace-separation-does-not-prevent-a)
- [Flatpak path traversal in files/etc directory during app deployment](https://junglewise.ai/threats/cve-2026-97024-a-path-traversal-vulnerability-in-flatpak-s-handling-of-the-files)
- [Flatpak path traversal in export/bin directory handling](https://junglewise.ai/threats/cve-2026-97023-a-path-traversal-vulnerability-in-flatpak-s-handling-of-the)
- [Flatpak heap buffer overflow in OCI delta stream parser](https://junglewise.ai/threats/cve-2026-96280-the-oci-delta-stream-parser-read-sizes-as-guint64-but-passed-them)