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.
https://access.redhat.com/errata/RHSA-2026:95493
https://access.redhat.com/errata/RHSA-2026:92369
https://access.redhat.com/errata/RHSA-2026:92221
https://access.redhat.com/errata/RHSA-2026:90364
https://access.redhat.com/errata/RHSA-2026:89733
https://access.redhat.com/errata/RHSA-2026:80687