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CVE-2026-43492

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

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.140, 6.12.88, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in a1793a48881ec8d26e9c79b0ee65753f1c6846a4; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 6d63615c796c085b4984e3031b9fa77fffb47360; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 2aa77a18dc7f2670497fe3ee5acbeda0b57659e5; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 26d3a97ad46c7a9226ec04d4bf35bd4998a97d16; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 8637dfb4c1d8a7026ef681f2477c6de8b71c4003; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 30e513e755bb381afce6fb57cdc8694136193f22; From 2d4d1eea540b27c72488fd1914674c42473d53df · fixed in 8c2f1288250a90a4b5cabed5d888d7e3aeed4035

  • Linux Linux

    4.4

  • KernelLinux

    From 4.4.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.140; From 6.7.0 · fixed in 6.12.88; From 6.13.0 · fixed in 6.18.30; From 6.19.0 · fixed in 7.0.7

References 8

git.kernel.org