---
id: "CVE-2026-99037"
kind: "vulnerability"
aliases: ["CVE-2026-99037"]
title: "Linux kernel: dm-crypt lmk mode with AEAD ciphers crashes on load"
severity: "low"
cvss: null
epss: 0.00209
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["dm-crypt", "kernel", "linux", "runtime", "self-hosted"]
not_affected_if: ["default-config", "no-lmk-table", "non-root-only"]
published_at: "2026-10-23T13:17:26+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-2026-99037", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-99037", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: dm-crypt lmk mode with AEAD ciphers crashes on load

Loading a dm-crypt table that pairs an AEAD cipher with the lmk IV mode makes the kernel read past a transform array and oops. The kernel project states only root can trigger it, so the impact is a local crash rather than privilege gain.

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

## How to check

- `uname -r` to see the running kernel version
- `dmsetup table` to look for crypt targets using `capi:` ciphers with `-lmk` and an AEAD cipher such as `gcm(aes)`

## Fix

- Update to a Linux kernel release that includes the upstream dm-crypt fix; the sources do not list fixed version numbers
- Avoid `lmk` IV mode with AEAD ciphers in dm-crypt tables until patched

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99037
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-99037

## From the sources

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

dm-crypt: reject the lmk IV mode with AEAD ciphers

A "capi:" table line that pairs an AEAD cipher with the lmk IV mode,
for example "capi:gcm(aes)-lmk" with the integrity:28:aead option,
causes an oops when it is loaded. lmk sets tfms_count to 64, but
crypt_alloc_tfms_aead only allocates one transform, so crypt_setkey
reads past the end of the tfms_aead array and calls crypto_aead_setkey
on the values it finds there.

lmk exists for compatibility with Loop-AES, which uses CBC, so refuse
it with an AEAD cipher rather than allocate 64 AEAD transforms. The
check cannot go in crypt_iv_lmk_ctr with the other lmk checks, because
the IV constructor runs after crypt_set_key.

Note that this is not a security bug because the memory corruption can
only be triggered by root.

---

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