# CVE-2026-98214: selinux: recheck intermediate backing files on mprotect()

> Local attackers can bypass SELinux execute restrictions on nested overlay filesystems by using mprotect instead of mmap, requiring specific SELinux policies and nested mounts.

- **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 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106467, BELL-CVE-2026-98214, DEBIAN-CVE-2026-98214, GHSA-cwv8-mjrx-v4v5, UBUNTU-CVE-2026-98214

## What is CVE-2026-98214?

CVE-2026-98214 is a vulnerability in Linux, published on 6 Oct 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:

selinux: recheck intermediate backing files on mprotect()

mprotect() can be used to bypass the SELinux checks that mmap() performs
against the intermediate layers of a stacked filesystem.

mmap() checks every backing layer as the request descends through the
stack.  mprotect() only has the lowest backing file in vma->vm_file, so it
rechecks the top-level user and the lowest mounter, but skips the mounters
of every layer in between.  With two nested overlayfs mounts and a policy
denying mounter_t -> middle_file_t:file { execute }, a direct
mmap(PROT_EXEC) is denied:

  avc:  denied  { execute } for  pid=71 comm="nested_exec"
    path="/payload" dev="overlay" ino=9
    scontext=user_u:base_r:mounter_t
    tcontext=user_u:object_r:middle_file_t tclass=file permissive=0

while mmap(PROT_NONE) followed by mprotect(PROT_EXEC) succeeds.

Preserve each intermediate path, mounter SID and file-description SID in
the backing-file security blob, copying the saved entries when another
backing layer is opened.  Allocate the array only for nested backing files,
and release it and the path references in the backing_file_free hook.

During mprotect(), recheck fd { use } and the requested inode permissions
for every saved mounter, and include the intermediate layers in the execmod
checks.  Policy for nested stacking may then need to grant intermediate
mounters what a direct mmap() already requires, and execmod on intermediate
labels for binaries using text relocations.

Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built
SELinux policy, on a mainline tree containing
commit f2381b546e7e ("fs: fix user path of nested backing files").

[PM: subject tweak]

## Which versions are affected by CVE-2026-98214?


## How do I fix CVE-2026-98214?

Apply the vendor's patch.

## Is CVE-2026-98214 being exploited?

There is no known exploitation of CVE-2026-98214 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98214 and fix it if it is affected.

What it is: CVE-2026-98214 is a vulnerability in Linux, published on 6 Oct 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-2026-98214 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-2026-98214/ (Markdown: https://insights.sbomify.com/CVE-2026-98214/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98214
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98214
- OSV: https://osv.dev/vulnerability/CVE-2026-98214

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98214/
Summaries are generated and may contain mistakes; the official description above is the record.