Fuse Project

fusermount in FUSE before 2.9.3-15 does not properly clear the environment before invoking (1) mount or (2) umount as root, which allows local users to write to arbitrary files via a crafted LIBMOUNT_MTAB environment variable that is used by mount's debugging feature.

FUSE, possibly 2.8.5 and earlier, allows local users to create mtab entries with arbitrary pathnames, and consequently unmount any filesystem, via a symlink attack on the parent directory of the mountpoint of a FUSE filesystem, a different vulnerability than CVE-2010-0789.

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.

libfuse is the reference implementation of the Linux FUSE. From version 3.18.0 to before version 3.18.2, a NULL pointer dereference and memory leak in fuse_uring_init_queue allows a local user to crash the FUSE daemon or cause resource exhaustion. When numa_alloc_local fails during io_uring queue entry setup, the code proceeds with NULL pointers. When fuse_uring_register_queue fails, NUMA allocations are leaked and the function incorrectly returns success. Only the io_uring transport is affected; the traditional /dev/fuse path is not affected. PoC confirmed with AddressSanitizer/LeakSanitizer. This issue has been patched in version 3.18.2.