# CVE-2022-49955: powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

> A flaw in Linux kernel RTAS handling on IBM Cell machines causes kernel crashes, leading to denial of service.

- **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:** 18 Jun 2025
- **Updated:** 23 May 2026
- **Also known as:** DEBIAN-CVE-2022-49955, GHSA-q32g-q8h6-hf4v, ROOT-OS-UBUNTU-2204-CVE-2022-49955, UBUNTU-CVE-2022-49955

## What is CVE-2022-49955?

CVE-2022-49955 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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:

powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

The semi-recent changes to MSR handling when entering RTAS (firmware)
cause crashes on IBM Cell machines. An example trace:

  kernel tried to execute user page (2fff01a8) - exploit attempt? (uid: 0)
  BUG: Unable to handle kernel instruction fetch
  Faulting instruction address: 0x2fff01a8
  Oops: Kernel access of bad area, sig: 11 [#1]
  BE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=4 NUMA Cell
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W          6.0.0-rc2-00433-gede0a8d3307a #207
  NIP:  000000002fff01a8 LR: 0000000000032608 CTR: 0000000000000000
  REGS: c0000000015236b0 TRAP: 0400   Tainted: G        W           (6.0.0-rc2-00433-gede0a8d3307a)
  MSR:  0000000008001002 <ME,RI>  CR: 00000000  XER: 20000000
  ...
  NIP 0x2fff01a8
  LR  0x32608
  Call Trace:
    0xc00000000143c5f8 (unreliable)
    .rtas_call+0x224/0x320
    .rtas_get_boot_time+0x70/0x150
    .read_persistent_clock64+0x114/0x140
    .read_persistent_wall_and_boot_offset+0x24/0x80
    .timekeeping_init+0x40/0x29c
    .start_kernel+0x674/0x8f0
    start_here_common+0x1c/0x50

Unlike PAPR platforms where RTAS is only used in guests, on the IBM Cell
machines Linux runs with MSR[HV] set but also uses RTAS, provided by
SLOF.

Fix it by copying the MSR[HV] bit from the MSR value we've just read
using mfmsr into the value used for RTAS.

It seems like we could also fix it using an #ifdef CELL to set MSR[HV],
but that doesn't work because it's possible to build a single kernel
image that runs on both Cell native and pseries.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2022-49955?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49955?

Apply the vendor's patch.

## Is CVE-2022-49955 being exploited?

There is no known exploitation of CVE-2022-49955 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-2022-49955 and fix it if it is affected.

What it is: CVE-2022-49955 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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-2022-49955 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-2022-49955/ (Markdown: https://insights.sbomify.com/CVE-2022-49955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49955
- OSV: https://osv.dev/vulnerability/CVE-2022-49955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49955/
Summaries are generated and may contain mistakes; the official description above is the record.