# CVE-2026-96280: Flatpak heap buffer overflow in OCI delta stream parser

Source: https://junglewise.ai/threats/cve-2026-96280-the-oci-delta-stream-parser-read-sizes-as-guint64-but-passed-them  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-27. Updated: 2026-09-27  
License: CC BY 4.0 with a link back

CVE-2026-96280 · Severity: high · CVSS 7.5 · Published 2026-09-27

Flatpak, a software application installer and sandbox system, contains a heap buffer overflow vulnerability in its OCI delta stream parser on 32-bit systems. An attacker controlling a malicious OCI registry can craft a specially crafted delta stream to trigger the overflow when a user installs or updates an application, potentially executing arbitrary code on the victim's system.

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

## Quick answers

**Is CVE-2026-96280 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96280 being exploited in the wild.

**How severe is CVE-2026-96280?** High severity, with a CVSS score of 7.5, published 27 September 2026.

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

**Is there a fix for CVE-2026-96280?** 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-2026-96280 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-96280?** 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

The vulnerability is a numeric truncation error (CWE-197) where the OCI delta stream parser reads allocation sizes as guint64 (64-bit) but passes them to GLib functions expecting gsize (32-bit on 32-bit systems), resulting in undersized heap allocations. Subsequent operations then use the original 64-bit size values, causing heap buffer overflow. The attack vector is network-based with high attack complexity due to platform-specific exploitation (32-bit only) and required user interaction to install/update applications.

## Affected products

- Flatpak Flatpak

## Timeline

- 2026-09-27: 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-2026-96280](https://access.redhat.com/security/cve/CVE-2026-96280)

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- [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 arbitrary file disclosure via OCI registry hardlink](https://junglewise.ai/threats/cve-2026-96279-a-malicious-oci-registry-can-hardlink-arbitrary-host-files-into)