# CVE-2026-98856: kprobes: Skip disarmed probes when checking optkprobe overlap

> A local attacker with high privileges can trigger memory corruption in the Linux kernel kprobes subsystem, potentially leading to arbitrary code execution or privilege escalation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108723, BELL-CVE-2026-98856, DEBIAN-CVE-2026-98856, GHSA-9hm5-vfv2-whh5, UBUNTU-CVE-2026-98856

## What is CVE-2026-98856?

CVE-2026-98856 is a memory corruption vulnerability in Linux, published on 18 Oct 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:

kprobes: Skip disarmed probes when checking optkprobe overlap

On x86, an optkprobe at A replaces five bytes with a jump. If a disabled
probe B is at A+2, get_optimized_kprobe() stops at B when arming a new
probe C at A+4. It leaves A optimized:

              A    A+1  A+2  A+3  A+4
  A's jump  | e9 | d0 | d1 | d2 | d3 |
  after C   | e9 | d0 | d1 | d2 | cc |

The INT3 for C overwrites the last byte of A's jump displacement, so
execution can jump to the wrong address. B can have prepared optinsns
while disarmed, but has no jump to unoptimize.

Continue past disarmed and unprepared probes to find the active optimized
probe before arming a probe in its jump.

## Which versions are affected by CVE-2026-98856?


## How do I fix CVE-2026-98856?

Apply the vendor's patch.

## Is CVE-2026-98856 being exploited?

There is no known exploitation of CVE-2026-98856 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98856 and fix it if it is affected.

What it is: CVE-2026-98856 is a memory corruption vulnerability in Linux, published on 18 Oct 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-2026-98856 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-2026-98856/ (Markdown: https://insights.sbomify.com/CVE-2026-98856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98856
- OSV: https://osv.dev/vulnerability/CVE-2026-98856

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98856/
Summaries are generated and may contain mistakes; the official description above is the record.