# CVE-2026-98923: arm64: io: Reject non-user protection in ioremap_prot()


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** BELL-CVE-2026-98923, DEBIAN-CVE-2026-98923, GHSA-q3vh-mmhj-mxhr, UBUNTU-CVE-2026-98923

## What is CVE-2026-98923?

CVE-2026-98923 is a vulnerability in Linux, published on 23 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

arm64: io: Reject non-user protection in ioremap_prot()

Mapping a stack-top page via /dev/mem with PROT_NONE and then
reading that process's /proc/<pid>/cmdline triggers a spurious WARN
in ioremap_prot() through generic_access_phys():

  WARNING: ./arch/arm64/include/asm/io.h:275 at generic_access_phys
  Call trace:
    generic_access_phys+0x1c8/0x228 (P)
    __access_remote_vm+0x2b4/0x398
    access_remote_vm+0x14/0x30
    get_mm_cmdline+0xf8/0x2a0
    proc_pid_cmdline_read+0x68/0x120

generic_access_phys() passes the protection derived from the user PTE
to ioremap_prot(). On arm64, a PROT_NONE mapping is represented by a
present-invalid PTE, so pte_present() still returns true and the
protection reaches ioremap_prot().

A PROT_NONE mapping does not have PTE_USER, causing the existing
WARN_ON_ONCE() in ioremap_prot() to fire even though this is a valid
user mapping. Execute-only mappings have the same issue and must not
be readable through this path either.

ioremap_prot() should therefore reject protection values without
PTE_USER without warning. This makes the access fail cleanly for
PROT_NONE and execute-only mappings while retaining the existing
user-protection contract.

## Which versions are affected by CVE-2026-98923?


## How do I fix CVE-2026-98923?

Upgrade to a fixed version.

## Is CVE-2026-98923 being exploited?

There is no known exploitation of CVE-2026-98923 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98923 and fix it if it is affected.

What it is: CVE-2026-98923 is a vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98923 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-2026-98923/ (Markdown: https://insights.sbomify.com/CVE-2026-98923/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98923
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98923
- OSV: https://osv.dev/vulnerability/CVE-2026-98923

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98923/
Summaries are generated and may contain mistakes; the official description above is the record.