# CVE-2022-49081: highmem: fix checks in __kmap_local_sched_{in,out}

> A logic error in Linux kernel highmem checks causes runtime warnings and potential instability when debug options are enabled.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 26 Feb 2025
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2022-49081, GHSA-v3gm-f9gf-wg97, UBUNTU-CVE-2022-49081

## What is CVE-2022-49081?

CVE-2022-49081 is a medium-severity denial of service vulnerability in Linux kernel, published on 26 Feb 2025. 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:

highmem: fix checks in __kmap_local_sched_{in,out}

When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out} check
that even slots in the tsk->kmap_ctrl.pteval are unmapped.  The slots are
initialized with 0 value, but the check is done with pte_none.  0 pte
however does not necessarily mean that pte_none will return true.  e.g.
on xtensa it returns false, resulting in the following runtime warnings:

 WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
 CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
 Call Trace:
   dump_stack+0xc/0x40
   __warn+0x8f/0x174
   warn_slowpath_fmt+0x48/0xac
   __kmap_local_sched_out+0x51/0x108
   __schedule+0x71a/0x9c4
   preempt_schedule_irq+0xa0/0xe0
   common_exception_return+0x5c/0x93
   do_wp_page+0x30e/0x330
   handle_mm_fault+0xa70/0xc3c
   do_page_fault+0x1d8/0x3c4
   common_exception+0x7f/0x7f

 WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
 CPU: 0 PID: 101 Comm: touch Tainted: G        W         5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
 Call Trace:
   dump_stack+0xc/0x40
   __warn+0x8f/0x174
   warn_slowpath_fmt+0x48/0xac
   __kmap_local_sched_in+0x50/0xe0
   finish_task_switch$isra$0+0x1ce/0x2f8
   __schedule+0x86e/0x9c4
   preempt_schedule_irq+0xa0/0xe0
   common_exception_return+0x5c/0x93
   do_wp_page+0x30e/0x330
   handle_mm_fault+0xa70/0xc3c
   do_page_fault+0x1d8/0x3c4
   common_exception+0x7f/0x7f

Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.

## Which versions are affected by CVE-2022-49081?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49081?

Apply the vendor's patch.

## Is CVE-2022-49081 being exploited?

There is no known exploitation of CVE-2022-49081 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-49081 and fix it if it is affected.

What it is: CVE-2022-49081 is a medium-severity denial of service vulnerability in Linux kernel, published on 26 Feb 2025. 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-2022-49081 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2022-49081/ (Markdown: https://insights.sbomify.com/CVE-2022-49081/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49081
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49081
- OSV: https://osv.dev/vulnerability/CVE-2022-49081

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49081/
Summaries are generated and may contain mistakes; the official description above is the record.