CVE-2026-64596 libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
Local attackers can bypass no-exec protections on pseudo filesystems like dma-buf, potentially enabling code execution if combined with other flaws.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64596?
CVE-2026-64596 is a vulnerability in Linux, published on 6 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
Since commit 1e7ab6f67824 ("anon_inode: rework assertions"), path_noexec() warns when an anonymous-inode file is mmap'd from a superblock that has not set SB_I_NOEXEC. dma-buf backs its files this way and never set the flag, so mmap of any exported buffer trips the warning on a CONFIG_DEBUG_VFS=y kernel:
WARNING: CPU: 11 PID: 121813 at fs/exec.c:118 path_noexec+0x47/0x50 do_mmap+0x2b5/0x680 vm_mmap_pgoff+0x129/0x210 ksys_mmap_pgoff+0x177/0x240 __x64_sys_mmap+0x33/0x70
init_pseudo() sets up internal SB_NOUSER mounts that are never path-reachable. Set both flags here so every pseudo filesystem gets them by default instead of each caller setting them.
SB_I_NODEV is inert for unreachable mounts. SB_I_NOEXEC has one visible effect: an executable mapping of a pseudo-fs fd, such as a dma-buf, now fails with -EPERM, which is the invariant the assertion enforces. No in-tree caller maps these executable.
Reproduce on CONFIG_DEBUG_VFS=y:
make -C tools/testing/selftests/dmabuf-heaps sudo ./tools/testing/selftests/dmabuf-heaps/dmabuf-heap -t system
Which versions are affected by CVE-2026-64596?
How do I fix CVE-2026-64596?
Apply the vendor's patch.
Is CVE-2026-64596 being exploited?
There is no known exploitation of CVE-2026-64596 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-64596, DEBIAN-CVE-2026-64596, GHSA-99j8-6mjv-5hff, UBUNTU-CVE-2026-64596.