---
id: "CVE-2026-98868"
kind: "vulnerability"
aliases: ["CVE-2026-98868"]
title: "Linux kernel dm-pcache: forged kset size crashes the system via BUG_ON"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["device-mapper", "dm-pcache", "kernel", "linux", "runtime"]
not_affected_if: ["dm-pcache-not-used", "module-not-loaded"]
published_at: "2026-10-18T16:17:41+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:12:47+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98868", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel dm-pcache: forged kset size crashes the system via BUG_ON

A forged key count in a dm-pcache cache segment makes the kernel advance past the segment's end during cache replay, writeback and GC. This trips a BUG_ON in cache_pos_advance(), which crashes the kernel.

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

## How to check

- Check whether the kernel has the dm-pcache module loaded with `lsmod | grep dm_pcache`
- Check the running kernel version with `uname -r` and compare it against the fixed release in the kernel stable tree
- unknown for a specific fixed version, as the sources do not say

## Fix

- Update the Linux kernel to a release that includes the commit rejecting a kset that overruns its segment
- unknown for the exact version, as the sources do not say

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98868

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

dm-pcache: reject a kset that overruns its segment

cache_replay(), the writeback worker and the GC worker read a kset of
get_kset_onmedia_size() bytes and advance the position by it. A forged
key_num makes that size exceed the segment's remaining space, so the
advance walks past the segment and trips the cache_pos_advance() BUG_ON.

Reject a kset whose on-media size exceeds cache_seg_remain() before use.

---

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