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… (CVE-2026-99037)

The Linux kernel's dm-crypt module had a flaw where pairing an AEAD cipher with the lmk IV mode (e.g., "capi:gcm(aes)-lmk") caused a kernel oops. The lmk mode sets tfms_count to 64, but crypt_alloc_tfms_aead allocates only one transform. Consequently, crypt_setkey reads beyond the allocated array and calls crypto_aead_setkey on invalid memory. The lmk mode exists for compatibility with Loop-AES, which uses CBC mode, so the fix was to reject lmk IV mode when used with AEAD ciphers rather than allocating 64 transforms. This check cannot be placed in the usual IV constructor due to ordering of operations. The vulnerability requires root access to trigger and thus is not considered a security bug.

The impact is limited to a kernel oops (crash) triggered by root users when loading a specific dm-crypt configuration combining AEAD ciphers with the lmk IV mode. There is no indication of privilege escalation or arbitrary code execution. Since root privileges are required to trigger the issue, it does not represent a direct security breach or escalation vector.

A fix has been implemented in the Linux kernel to reject the use of the lmk IV mode with AEAD ciphers, preventing the out-of-bounds access and kernel oops. Users should update to a kernel version that includes this fix. No additional mitigation is required as the vulnerability cannot be triggered without root privileges.