libfuse is the reference implementation of the Linux FUSE. From version 3.18.0 to before version 3.18.2, a use-after-free vulnerability in the io_uring subsystem of libfuse allows a local attacker to crash FUSE filesystem processes and potentially execute arbitrary code. When io_uring thread creation fails due to resource exhaustion (e.g., cgroup pids.max), fuse_uring_start() frees the ring pool structure but stores the dangling pointer in the session state, leading to a use-after-free when the session shuts down. The trigger is reliable in containerized environments where cgroup pids.max limits naturally constrain thread creation. This issue has been patched in version 3.18.2.
Weakness
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Libfuse | Libfuse_project | 3.18.0 (including) | 3.18.2 (excluding) |
| Fuse3 | Ubuntu | resolute | * |
| Fuse3 | Ubuntu | upstream | * |
Potential Mitigations
References
- https://github.com/libfuse/libfuse/commit/49fcd891a58f622c098e2ca67d66086f7b213836
- https://github.com/libfuse/libfuse/releases/tag/fuse-3.18.2
- https://github.com/libfuse/libfuse/security/advisories/GHSA-qxv7-xrc2-qmfx
- https://access.redhat.com/security/cve/CVE-2026-33150
- https://bugzilla.redhat.com/show_bug.cgi?id=2449771
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33150.json