---
id: "CVE-2026-98941"
kind: "vulnerability"
aliases: ["CVE-2026-98941"]
title: "Linux kernel ext4: encrypted files on large folios crash the system"
severity: "unknown"
cvss: null
epss: 0.0019
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ext4", "file-servers", "linux-kernel", "runtime", "self-hosted"]
not_affected_if: ["encrypt-set-at-mkfs-or-mount", "kernel-v7.3-or-later", "no-ext4-encryption"]
published_at: "2026-10-23T13:17:15+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98941", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-98941", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel ext4: encrypted files on large folios crash the system

Enabling the encrypt feature on a mounted ext4 filesystem bypasses a mount-time check, so writing encrypted data can trigger a kernel NULL pointer dereference and crash. The fix disables large folios on encrypted inodes, as already done for data-journaling inodes.

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

## How to check

- `uname -r` to see whether the running kernel is between v6.19 and v7.2
- `tune2fs -l /dev/sdX | grep features` to check whether the `encrypt` feature is enabled on a mounted ext4 filesystem
- unknown whether the sources give a further exposure check

## Fix

- Update the Linux kernel to a release that includes the ext4 encrypted-inode large folio fix; the exact version is unknown from the sources
- Kernels from v7.3 onward are not affected by this bug, per the description

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98941
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-98941

## From the sources

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

ext4: don't enable large folios on encrypted inodes

Commit 709f0f1f1bf5 ("ext4: add checks for large folio
incompatibilities when BS > PS") disables large folios at mount time
if the "encrypt" feature is set. However, enabling that feature on a
mounted filesystem circumvents that check, and writing encrypted data
results in a crash:

  BUG: kernel NULL pointer dereference, address: 0000000000000028
  Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
  RIP: 0010:ext4_finish_bio+0xf7/0x3e0
  Call Trace:
   ext4_release_io_end+0x51/0x110
   ext4_end_io_end+0x4c/0xe0
   ext4_end_io_rsv_work+0xb3/0x100

Fix this by disabling large folios on encrypted inodes, as is
already done for inodes that use data journaling.

This affects all kernels between v6.19 and v7.2, but it is not needed
in v7.3, where the code was significantly refactored.

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