# CVE-2025-71109: MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits

> A buffer overflow in the MIPS ftrace implementation causes memory corruption and kernel hangs when the kernel is located beyond 32 bits.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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:** 14 Jan 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2025-71109, DEBIAN-CVE-2025-71109, GHSA-f8h3-qj6h-j2cj, ROOT-OS-DEBIAN-11-CVE-2025-71109, ROOT-OS-DEBIAN-12-CVE-2025-71109, ROOT-OS-DEBIAN-13-CVE-2025-71109, ROOT-OS-UBUNTU-2204-CVE-2025-71109, ROOT-OS-UBUNTU-2404-CVE-2025-71109, UBUNTU-CVE-2025-71109

## What is CVE-2025-71109?

CVE-2025-71109 is a high-severity memory corruption vulnerability in Linux kernel, published on 14 Jan 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:

MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits

Since commit e424054000878 ("MIPS: Tracing: Reduce the overhead of
dynamic Function Tracer"), the macro UASM_i_LA_mostly has been used,
and this macro can generate more than 2 instructions. At the same
time, the code in ftrace assumes that no more than 2 instructions can
be generated, which is why it stores them in an int[2] array. However,
as previously noted, the macro UASM_i_LA_mostly (and now UASM_i_LA)
causes a buffer overflow when _mcount is beyond 32 bits. This leads to
corruption of the variables located in the __read_mostly section.

This corruption was observed because the variable
__cpu_primary_thread_mask was corrupted, causing a hang very early
during boot.

This fix prevents the corruption by avoiding the generation of
instructions if they could exceed 2 instructions in
length. Fortunately, insn_la_mcount is only used if the instrumented
code is located outside the kernel code section, so dynamic ftrace can
still be used, albeit in a more limited scope. This is still
preferable to corrupting memory and/or crashing the kernel.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2025-71109?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-71109?

Apply the vendor's patch.

## Is CVE-2025-71109 being exploited?

There is no known exploitation of CVE-2025-71109 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-2025-71109 and fix it if it is affected.

What it is: CVE-2025-71109 is a high-severity memory corruption vulnerability in Linux kernel, published on 14 Jan 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-2025-71109 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-2025-71109/ (Markdown: https://insights.sbomify.com/CVE-2025-71109/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71109
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71109
- OSV: https://osv.dev/vulnerability/CVE-2025-71109

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71109/
Summaries are generated and may contain mistakes; the official description above is the record.