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CVE-2025-40052 json

smb: client: fix crypto buffers in non-linear memory

published 2025-10-28 12 mo ago modified 2026-10-19 20 d ago also EUVD-2025-36476

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

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

smb: client: fix crypto buffers in non-linear memory

The crypto API, through the scatterlist API, expects input buffers to be in linear memory. We handle this with the cifs_sg_set_buf() helper that converts vmalloc'd memory to their corresponding pages.

However, when we allocate our aead_request buffer (@creq in smb2ops.c::crypt_message()), we do so with kvzalloc(), which possibly puts aead_request->__ctx in vmalloc area.

AEAD algorithm then uses ->__ctx for its private/internal data and operations, and uses sg_set_buf() for such data on a few places.

This works fine as long as @creq falls into kmalloc zone (small requests) or vmalloc'd memory is still within linear range.

Tasks' stacks are vmalloc'd by default (CONFIG_VMAP_STACK=y), so too many tasks will increment the base stacks' addresses to a point where virt_addr_valid(buf) will fail (BUG() in sg_set_buf()) when that happens.

In practice: too many parallel reads and writes on an encrypted mount will trigger this bug.

To fix this, always alloc @creq with kmalloc() instead. Also drop the @sensitive_size variable/arguments since kfree_sensitive() doesn't need it.

Backtrace:

[ 945.272081] ------------[ cut here ]------------ [ 945.272774] kernel BUG at include/linux/scatterlist.h:209! [ 945.273520] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI [ 945.274412] CPU: 7 UID: 0 PID: 56 Comm: kworker/u33:0 Kdump: loaded Not tainted 6.15.0-lku-11779-g8e9d6efccdd7-dirty #1 PREEMPT(voluntary) [ 945.275736] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014 [ 945.276877] Workqueue: writeback wb_workfn (flush-cifs-2) [ 945.277457] RIP: 0010:crypto_gcm_init_common+0x1f9/0x220 [ 945.278018] Code: b0 00 00 00 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 c7 c0 00 00 00 80 48 2b 05 5c 58 e5 00 e9 58 ff ff ff <0f> 0b 0f 0b 0f 0b 0f 0b 0f 0b 0f 0b 48 c7 04 24 01 00 00 00 48 8b [ 945.279992] RSP: 0018:ffffc90000a27360 EFLAGS: 00010246 [ 945.280578] RAX: 0000000000000000 RBX: ffffc90001d85060 RCX: 0000000000000030 [ 945.281376] RDX: 0000000000080000 RSI: 0000000000000000 RDI: ffffc90081d85070 [ 945.282145] RBP: ffffc90001d85010 R08: ffffc90001d85000 R09: 0000000000000000 [ 945.282898] R10: ffffc90001d85090 R11: 0000000000001000 R12: ffffc90001d85070 [ 945.283656] R13: ffff888113522948 R14: ffffc90001d85060 R15: ffffc90001d85010 [ 945.284407] FS: 0000000000000000(0000) GS:ffff8882e66cf000(0000) knlGS:0000000000000000 [ 945.285262] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 945.285884] CR2: 00007fa7ffdd31f4 CR3: 000000010540d000 CR4: 0000000000350ef0 [ 945.286683] Call Trace: [ 945.286952] <TASK> [ 945.287184] ? crypt_message+0x33f/0xad0 [cifs] [ 945.287719] crypto_gcm_encrypt+0x36/0xe0 [ 945.288152] crypt_message+0x54a/0xad0 [cifs] [ 945.288724] smb3_init_transform_rq+0x277/0x300 [cifs] [ 945.289300] smb_send_rqst+0xa3/0x160 [cifs] [ 945.289944] cifs_call_async+0x178/0x340 [cifs] [ 945.290514] ? __pfx_smb2_writev_callback+0x10/0x10 [cifs] [ 945.291177] smb2_async_writev+0x3e3/0x670 [cifs] [ 945.291759] ? find_held_lock+0x32/0x90 [ 945.292212] ? netfs_advance_write+0xf2/0x310 [ 945.292723] netfs_advance_write+0xf2/0x310 [ 945.293210] netfs_write_folio+0x346/0xcc0 [ 945.293689] ? __pfx__raw_spin_unlock_irq+0x10/0x10 [ 945.294250] netfs_writepages+0x117/0x460 [ 945.294724] do_writepages+0xbe/0x170 [ 945.295152] ? find_held_lock+0x32/0x90 [ 945.295600] ? kvm_sched_clock_read+0x11/0x20 [ 945.296103] __writeback_single_inode+0x56/0x4b0 [ 945.296643] writeback_sb_inodes+0x229/0x550 [ 945.297140] __writeback_inodes_wb+0x4c/0xe0 [ 945.297642] wb_writeback+0x2f1/0x3f0 [ 945.298069] wb_workfn+0x300/0x490 [ 945.298472] process_one_work+0x1fe/0x590 [ 945.298949] worker_thread+0x1ce/0x3c0 [ 945.299397] ? __pfx_worker_thread+0x10/0x10 [ 945.299900] kthr ---truncated---

Patch / fix

  • Linux Linux 6.6.112, 6.12.53, 6.17.3, 6.18
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.17.6-1

debian advisories DEBIAN-CVE-2025-40052

  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-gcp Ubuntu 25.10 6.17.0-1007.7
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1048.53
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1049.49

ubuntu advisories UBUNTU-CVE-2025-40052

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.58.1
  • kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.58.1
  • kernel-rt_debug Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.58.1
  • kernel-source-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.58.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.7.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.7.1

suse advisories SUSE-SU-2025:4301-1SUSE-SU-2025:21080-1SUSE-SU-2025:21147-1SUSE-SU-2025:21180-1SUSE-SU-2026:20561-1SUSE-SU-2025:21052-1

  • kernel-source-longterm openSUSE Tumbleweed 6.18.16-1.1
  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.7.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.7.1

opensuse advisories openSUSE-SU-2026:10301-1openSUSE-SU-2025:20091-1openSUSE-SU-2025:15702-1

  • kernel Azure Linux 3.0 6.6.112.1-2

azure linux advisories AZL-68846

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-40052 updated cvss 6.2

kernel: smb: client: fix crypto buffers in non-linear memory

  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.