CVE-2026-43492 lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl()

What is CVE-2026-43492?

CVE-2026-43492 is a medium-severity vulnerability in Linux kernel, published on 19 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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 system call with a larger "out_len" than "in_len" and filling the "in" buffer with zeroes, crypto_akcipher_sync_prep() will create an all-zero scatterlist used for both the "src" and "dst" member of struct akcipher_request and thereby fulfil the conditions to trigger the bug:

sys_keyctl() keyctl_pkey_e_d_s() asymmetric_key_eds_op() software_key_eds_op() crypto_akcipher_sync_encrypt() crypto_akcipher_sync_prep() crypto_akcipher_encrypt() rsa_enc() mpi_read_raw_from_sgl()

To the user this will be visible as a DoS as the kernel spins forever, causing soft lockup splats as a side effect.

Fix it.

Weakness: CWE-190

Which versions are affected by CVE-2026-43492?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-43492?

Apply the vendor's patch.

Is CVE-2026-43492 being exploited?

There is no known exploitation of CVE-2026-43492 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-86975, BELL-CVE-2026-43492, DEBIAN-CVE-2026-43492, GHSA-q8fh-4v85-p8mj, ROOT-OS-DEBIAN-11-CVE-2026-43492, ROOT-OS-DEBIAN-12-CVE-2026-43492 and 3 more.