CVE-2026-96280
Description
The OCI delta stream parser read sizes as guint64 but passed them to GLib I/O and allocation functions expecting gsize (32 bits on 32-bit systems), causing undersized allocations while subsequent operations use the original 64-bit size, leading to heap buffer overflows. An attacker controlling an OCI registry can craft a delta stream that triggers this during flatpak install/update, potentially achieving code execution on 32-bit systems.
Statement
Red Hat estimates the CVSSv3.1 vector of CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
The malicious stream is served over the network (AV:N), and the attacker needs only control over the OCI registry content (PR:N). The OCI delta stream parser reads sizes as a 64-bit guint64 but passes them to GLib I/O and allocation functions expecting gsize; on 32-bit systems gsize is only 32 bits wide, so the value is silently truncated, producing an undersized allocation while later operations still use the original 64-bit size, leading to a heap buffer overflow. This overflow only manifests on 32-bit targets — on 64-bit systems gsize and guint64 are the same width and truncation does not occur, so exploitability depends on a target configuration outside the attacker's control (AC:H). Meaningful user interaction is required (UI:R).
The vulnerable and impacted components remain within the same flatpak client/helper security authority (S:U). Because this is a heap buffer overflow with a stated path to code execution in the Flatpak client process, a successful exploit is treated as a full compromise of that process's privileges (C:H/I:H/A:H).
Mitigation
Only install applications from trusted OCI registries. Flatpak remotes using the default OSTree transport are not affected.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Acknowledgements
Upstream acknowledges Sebastian Wick as the original reporter.
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