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Linux CVE-2026-23374

| EUVDEUVD-2026-15363 MEDIUM
2026-03-25 Linux GHSA-w776-5fwp-835q
Information Disclosure Linux
5.5
CVSS 3.1 · NVD
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Vulnerability Assessment

Impact

The risk assessment is nuanced. While CVSS and EPSS scores are not provided, the vulnerability exhibits several important characteristics: (1) Attack Vector is LOCAL only (process must submit block I/O operations), (2) Privileges Required is LOW (any user can trigger via block device reads/writes), (3) User Interaction is NOT required, (4) Scope is UNCHANGED (affects only the kernel), (5) Confidentiality/Integrity/Availability impact varies—the bug manifests as kernel BUG warnings and potential data corruption in trace buffers, suggesting MODERATE to HIGH availability impact (kernel panic risk) but potentially LOW confidentiality impact. The vulnerability is NOT in the KEV catalog and has no public exploit code beyond the test case that triggered it. However, reproducibility is HIGH (blktests reliably triggers it on PREEMPT(full) kernels). The technical impact is significant for systems with kernel tracing enabled, but the vulnerability requires specific configuration (PREEMPT(full), blktrace enabled) to manifest. Real-world risk is MODERATE: it affects production servers using kernel tracing for performance analysis, but is easily mitigated via patching and is not remotely exploitable.
Exploit ScenarioDerived

An attacker or unprivileged user on a system with kernel block I/O tracing enabled can trigger the vulnerability by performing simple block device read operations (e.g., dd if=/dev/null bs=4096 count=256) from user-space process context. The kernel's blktrace subsystem attempts to record command-line information via tracing_record_cmdline() without ensuring preemption is disabled, causing __this_cpu_read() to trigger a BUG warning when CONFIG_DEBUG_PREEMPT detects the context violation. While this does not directly expose sensitive data via information disclosure, repeated triggering can cause kernel panics or data corruption in trace buffers, resulting in denial of service. On systems with PREEMPT(full) enabled (common in real-time or high-latency-sensitive environments), this becomes a trivial denial of service vector requiring no special privileges beyond basic user I/O operations.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 25, 2026

This vulnerability is a preemption context violation in the Linux kernel's block I/O tracing subsystem where tracing_record_cmdline() unsafely uses __this_cpu_read() and __this_cpu_write() operations from preemptible context. The Linux kernel in versions supporting blktrace (affected via CPE cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*) is vulnerable, allowing potential information disclosure or denial of service when block tracing is enabled and block I/O operations occur from user-space processes. This is not actively exploited in the wild (no KEV status), but the vulnerability has functional proof of concept through blktests/blktrace/002, making it a moderate priority for kernel maintainers and distributions shipping PREEMPT(full) configurations.

RemediationAI

Apply the Linux kernel patch available at https://git.kernel.org/stable/c/59efa088752b1c380a0475974679850cc8aef907 or https://git.kernel.org/stable/c/da46b5dfef48658d03347cda21532bcdbb521e67, or upgrade to a kernel version that includes these commits. The fix involves moving the tracing_record_cmdline() call to a context where preemption is safely disabled, or wrapping the call with appropriate preemption-disabled sections. Until patching is possible, disable kernel block I/O tracing by ensuring blktrace is not actively collecting traces (echo 0 > /sys/kernel/debug/tracing/events/block/enable or rmmod blk_tracer). For production systems with critical tracing requirements, prioritize kernel patching over workarounds. Verify the fix is included in your Linux distribution's kernel update and perform regression testing with your workload to ensure trace functionality remains intact post-patch.

Affected VersionsENISA

Linux patch: 0
Linux 7ffbd48d5cab22bcd1120eb2349db1319e2d827a <59efa088752b1c380a0475974679850cc8aef907
Linux 3.8
Linux patch: 6.19.7
Linux patch: 7.0-rc3
Linux 7ffbd48d5cab22bcd1120eb2349db1319e2d827a <da46b5dfef48658d03347cda21532bcdbb521e67

Affected Packages

euvd linux no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Technical ContextAI · show details

The vulnerability resides in the Linux kernel's block I/O tracing infrastructure (blktrace), specifically in functions like __blk_add_trace(), blk_add_trace_plug(), blk_add_trace_unplug(), and blk_add_trace_rq(). These functions call tracing_record_cmdline(current) early in their execution path before ring buffer reservation, from process context where preemption is fully enabled. The underlying issue is that tracing_record_cmdline() uses per-CPU operations (__this_cpu_read() and __this_cpu_write()) on the trace_cmdline_save variable and explicitly asserts preemption is disabled via lockdep_assert_preemption_disabled(). These per-CPU operations are atomic only when preemption is disabled, as they were originally designed for scheduler context (probe_wakeup_sched_switch() and probe_wakeup()). When called from preemptible context, a context switch could occur between the per-CPU read and write operations, corrupting the per-CPU variable or causing kernel panics. The root cause is a missing preemption context safety check, classifiable as improper synchronization or concurrency control.

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Severity by source

NVD PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SUSE 5.2 MEDIUM
Red Hat 5.5 LOW

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

3
CVSS changed
Apr 24, 2026 - 16:37 NVD
5.5 (MEDIUM)
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
CVE Published
Mar 25, 2026 - 10:27 nvd
N/A

DescriptionNVD

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

blktrace: fix __this_cpu_read/write in preemptible context

tracing_record_cmdline() internally uses __this_cpu_read() and __this_cpu_write() on the per-CPU variable trace_cmdline_save, and trace_save_cmdline() explicitly asserts preemption is disabled via lockdep_assert_preemption_disabled(). These operations are only safe when preemption is off, as they were designed to be called from the scheduler context (probe_wakeup_sched_switch() / probe_wakeup()).

__blk_add_trace() was calling tracing_record_cmdline(current) early in the blk_tracer path, before ring buffer reservation, from process context where preemption is fully enabled. This triggers the following using blktests/blktrace/002:

blktrace/002 (blktrace ftrace corruption with sysfs trace) [failed] runtime 0.367s ... 0.437s something found in dmesg: [ 81.211018] run blktests blktrace/002 at 2026-02-25 22:24:33 [ 81.239580] null_blk: disk nullb1 created [ 81.357294] BUG: using __this_cpu_read() in preemptible [00000000] code: dd/2516 [ 81.362842] caller is tracing_record_cmdline+0x10/0x40 [ 81.362872] CPU: 16 UID: 0 PID: 2516 Comm: dd Tainted: G N 7.0.0-rc1lblk+ #84 PREEMPT(full) [ 81.362877] Tainted: [N]=TEST [ 81.362878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 81.362881] Call Trace: [ 81.362884] <TASK> [ 81.362886] dump_stack_lvl+0x8d/0xb0 ... (See '/mnt/sda/blktests/results/nodev/blktrace/002.dmesg' for the entire message)

[ 81.211018] run blktests blktrace/002 at 2026-02-25 22:24:33 [ 81.239580] null_blk: disk nullb1 created [ 81.357294] BUG: using __this_cpu_read() in preemptible [00000000] code: dd/2516 [ 81.362842] caller is tracing_record_cmdline+0x10/0x40 [ 81.362872] CPU: 16 UID: 0 PID: 2516 Comm: dd Tainted: G N 7.0.0-rc1lblk+ #84 PREEMPT(full) [ 81.362877] Tainted: [N]=TEST [ 81.362878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 81.362881] Call Trace: [ 81.362884] <TASK> [ 81.362886] dump_stack_lvl+0x8d/0xb0 [ 81.362895] check_preemption_disabled+0xce/0xe0 [ 81.362902] tracing_record_cmdline+0x10/0x40 [ 81.362923] __blk_add_trace+0x307/0x5d0 [ 81.362934] ? lock_acquire+0xe0/0x300 [ 81.362940] ? iov_iter_extract_pages+0x101/0xa30 [ 81.362959] blk_add_trace_bio+0x106/0x1e0 [ 81.362968] submit_bio_noacct_nocheck+0x24b/0x3a0 [ 81.362979] ? lockdep_init_map_type+0x58/0x260 [ 81.362988] submit_bio_wait+0x56/0x90 [ 81.363009] __blkdev_direct_IO_simple+0x16c/0x250 [ 81.363026] ? __pfx_submit_bio_wait_endio+0x10/0x10 [ 81.363038] ? rcu_read_lock_any_held+0x73/0xa0 [ 81.363051] blkdev_read_iter+0xc1/0x140 [ 81.363059] vfs_read+0x20b/0x330 [ 81.363083] ksys_read+0x67/0xe0 [ 81.363090] do_syscall_64+0xbf/0xf00 [ 81.363102] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 81.363106] RIP: 0033:0x7f281906029d [ 81.363111] Code: 31 c0 e9 c6 fe ff ff 50 48 8d 3d 66 63 0a 00 e8 59 ff 01 00 66 0f 1f 84 00 00 00 00 00 80 3d 41 33 0e 00 00 74 17 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 5b c3 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec [ 81.363113] RSP: 002b:00007ffca127dd48 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 81.363120] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f281906029d [ 81.363122] RDX: 0000000000001000 RSI: 0000559f8bfae000 RDI: 0000000000000000 [ 81.363123] RBP: 0000000000001000 R08: 0000002863a10a81 R09: 00007f281915f000 [ 81.363124] R10: 00007f2818f77b60 R11: 0000000000000246 R12: 0000559f8bfae000 [ 81.363126] R13: 0000000000000000 R14: 0000000000000000 R15: 000000000000000a [ 81.363142] </TASK>

The same BUG fires from blk_add_trace_plug(), blk_add_trace_unplug(), and blk_add_trace_rq() paths as well.

The purpose of tracin ---truncated---

Threat Intelligence Overview

EPSS Score
0.0%
Top 95% exploitable
Data Quality
6 sources
Confidence: High
EUVD NVD CVE.org EPSS Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
9.8
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9.0
CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

Debian

linux
Release Status Fixed Version Urgency
bullseye vulnerable 5.10.223-1 -
bullseye (security) vulnerable 5.10.251-1 -
bookworm vulnerable 6.1.159-1 -
bookworm (security) vulnerable 6.1.164-1 -
trixie vulnerable 6.12.73-1 -
trixie (security) vulnerable 6.12.74-2 -
forky, sid fixed 6.19.8-1 -
(unstable) fixed 6.19.8-1 -

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-23374 ADVISORY https://ubuntu.com/security/notices/USN-8567-1 ADVISORY https://vuldb.com/vuln/353018 REF https://git.kernel.org/stable/c/37e86414cc9989344de82d2a658a095f8d5e71d9 REF https://git.kernel.org/stable/c/59efa088752b1c380a0475974679850cc8aef907 REF https://git.kernel.org/stable/c/6e5c3ddf17a2cb1722301bbbd15655fcc20ed1ce REF https://git.kernel.org/stable/c/aaba6ee63ba65b026401c94e2dd16b9f6e895934 REF https://git.kernel.org/stable/c/da46b5dfef48658d03347cda21532bcdbb521e67 REF https://git.kernel.org/stable/c/e5584932ac1dacc182c430d09e2b5490d1d4372b

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