# CVE-2026-89905: LoongArch: BPF: Move arena register slot below TCC context

> A memory corruption vulnerability in the Linux kernel's LoongArch BPF implementation allows local attackers to potentially execute code or escalate privileges when arena features are enabled.

- **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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89905, GHSA-74m2-6pj4-prfm, UBUNTU-CVE-2026-89905

## What is CVE-2026-89905?

CVE-2026-89905 is a memory corruption vulnerability in Linux, published on 16 Sep 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:

LoongArch: BPF: Move arena register slot below TCC context

Currently, the stack layout places the optional arena register slot
above the tail call counter context. When arena_vm_start is dynamically
enabled, it shifts the relative offset of the tcc_ptr slot within the
stack frame, causing hardcoded tracking macros to mismatch and leading
to memory misalignment or corruption potentially.

To fix this, move the arena register save and restore sequences below
the tail call counter context slots in both build_prologue() and the
epilogue.

Update __build_epilogue() to insert a proper offset decrement to safely
skip the unneeded tcc_ptr reading block while accurately aligning with
the relocated arena slot at the very bottom.

With this patch, the tcc_ptr slot is always positioned at a fixed
distance directly underneath the base callee-saved registers that is
independent of whether the arena features are on.

## Which versions are affected by CVE-2026-89905?


## How do I fix CVE-2026-89905?

Apply the vendor's patch.

## Is CVE-2026-89905 being exploited?

There is no known exploitation of CVE-2026-89905 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89905 and fix it if it is affected.

What it is: CVE-2026-89905 is a memory corruption vulnerability in Linux, published on 16 Sep 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-2026-89905 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-2026-89905/ (Markdown: https://insights.sbomify.com/CVE-2026-89905/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89905
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89905
- OSV: https://osv.dev/vulnerability/CVE-2026-89905

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89905/
Summaries are generated and may contain mistakes; the official description above is the record.