# CVE-2026-96276: Flatpak path traversal in build-init extension handling

Source: https://junglewise.ai/threats/cve-2026-96276-if-a-malicious-sdk-container-declares-an-extension-point-with-a  
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-2026-96276 · Severity: critical · CVSS 9.8 · Published 2026-09-23

Flatpak is a containerization technology used by developers to build and package applications. When a developer uses a malicious or compromised SDK with the build-init command, an attacker can write arbitrary files outside the intended working directory on the developer's system, potentially compromising the build environment and enabling code injection attacks.

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

## Quick answers

**Is CVE-2026-96276 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96276 being exploited in the wild.

**How severe is CVE-2026-96276?** Critical severity, with a CVSS score of 9.8, published 23 September 2026.

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

**Is there a fix for CVE-2026-96276?** A patch was published on 2026: Fixed in v1.18.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-96276 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-96276?** Check whether you run 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 path traversal vulnerability exists in Flatpak's build-init command when processing SDK extension points with crafted directory paths. The vulnerability allows the `..` directory traversal sequence to bypass pathname restrictions, enabling arbitrary file write operations in the host context. An attacker must provide a malicious SDK container that declares an extension point with a crafted path, and a developer must run `flatpak build-init --writable-sdk --sdk-extension` with that SDK.

## Affected products

- Flatpak Flatpak before 1.18.1

## Timeline

- 2026-09-23: disclosed
- 2026: patched: Fixed in v1.18.1

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-96276](https://access.redhat.com/security/cve/CVE-2026-96276)

## Related threats

- [Flatpak path traversal in system-helper via crafted architecture name](https://junglewise.ai/threats/cve-2026-92162-flatpak-is-a-system-for-building-distributing-and-running)
- [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)