# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 6 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64596, DEBIAN-CVE-2026-64596, GHSA-99j8-6mjv-5hff, UBUNTU-CVE-2026-64596

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64596 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-64596 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64596/ (Markdown: https://insights.sbomify.com/CVE-2026-64596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64596
- OSV: https://osv.dev/vulnerability/CVE-2026-64596

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64596/
Summaries are generated and may contain mistakes; the official description above is the record.