Bug 2539419 (CVE-2026-96280)

Summary:	CVE-2026-96280 flatpak: flatpak: Buffer overflow in OCI delta stream path names on 32-bit systems
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
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Doc Text:	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.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-23 14:02:14 UTC

GHSA-jr92-2v97-wgvc (https://github.com/flatpak/flatpak/security/advisories/GHSA-jr92-2v97-wgvc)

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). The silent truncation causes undersized allocations while subsequent operations use the original 64-bit size, leading to heap buffer overflows. On 64-bit systems, gsize and guint64 are the same width, so the truncation does not occur and the issue is not practically exploitable.

Mitigation: Only install applications from trusted OCI registries. Flatpak remotes using the default OSTree transport are not affected. Fixed in 1.18.1 (backports available for 1.16.x). Reported by @swick.