---
id: "CVE-2026-98856"
kind: "vulnerability"
aliases: ["CVE-2026-98856"]
title: "Linux kernel: kprobes overlap check can corrupt optimized jump and misroute execution"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "kprobes", "linux-kernel", "x86"]
not_affected_if: ["non-x86"]
published_at: "2026-10-18T16:17:40+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:12:57+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98856", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel: kprobes overlap check can corrupt optimized jump and misroute execution

In the Linux kernel's kprobes code on x86, arming a new probe can overwrite part of an existing optimized probe's jump, so execution can jump to the wrong address. The sources do not state a confirmed attacker outcome beyond wrong-address execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` and compare against a kernel build that includes the upstream fix for CVE-2026-98856
- Check whether kprobes or optimized kprobes are in use (unknown from the sources)

## Fix

- Update the Linux kernel to a release that includes the upstream kprobes fix for CVE-2026-98856 (exact versions unknown from the sources)

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98856

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_