CVE-2026-43492

/// Technical description

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

lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl()

Yiming reports an integer underflow in mpi_read_raw_from_sgl() when

subtracting "lzeros" from the unsigned "nbytes".

For this to happen, the scatterlist "sgl" needs to occupy more bytes

than the "nbytes" parameter and the first "nbytes + 1" bytes of the

scatterlist must be zero. Under these conditions, the while loop

iterating over the scatterlist will count more zeroes than "nbytes",

subtract the number of zeroes from "nbytes" and cause the underflow.

When commit 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") originally

introduced the bug, it couldn't be triggered because all callers of

mpi_read_raw_from_sgl() passed a scatterlist whose length was equal to

"nbytes".

However since commit 63ba4d67594a ("KEYS: asymmetric: Use new crypto

interface without scatterlists"), the underflow can now actually be

triggered. When invoking a KEYCTL_PKEY_ENCRYPT

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References