CVE-2026-43401

Description

In the Linux kernel, the following vulnerability has been resolved: cpufreq: intel_pstate: Fix NULL pointer dereference in update_cpu_qos_request() The update_cpu_qos_request() function attempts to initialize the 'freq' variable by dereferencing 'cpudata' before verifying if the 'policy' is valid. This issue occurs on systems booted with the "nosmt" parameter, where all_cpu_data[cpu] is NULL for the SMT sibling threads. As a result, any call to update_qos_requests() will result in a NULL pointer dereference as the code will attempt to access pstate.turbo_freq using the NULL cpudata pointer. Also, pstate.turbo_freq may be updated by intel_pstate_get_hwp_cap() after initializing the 'freq' variable, so it is better to defer the 'freq' until intel_pstate_get_hwp_cap() has been called. Fix this by deferring the 'freq' assignment until after the policy and driver_data have been validated. [ rjw: Added one paragraph to the changelog ]

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* - VULNERABLE

Linux Kernel (Specific versions prior to commits 42738dffb7b0766a45882dff7989401d78f66f92, 6bfda7ce56e7d14a677b7bcd6c7a5009cc29aa88, ab39cc4cb8ceecdc2b61747433e7237f1ac2b789)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#include <stdio.h>
#include <stdlib.h>

/*
 * PoC for CVE-2026-43401
 * Trigger: intel_pstate NULL pointer dereference
 * Condition: System must be booted with 'nosmt' parameter.
 * Description: Attempts to trigger cpufreq update paths.
 */

int main() {
    printf("[+] Attempting to trigger CVE-2026-43401\n");
    printf("[!] This PoC requires the system to be booted with 'nosmt'.\n");
    
    // Triggering cpufreq transitions might invoke update_cpu_qos_request()
    // Writing to scaling_setspeed or changing governors can trigger internal updates.
    system("cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq > /dev/null");
    
    // In a real exploit scenario, specific timing or sysfs manipulation is needed
    // to hit the exact code path where update_qos_requests() is called on a NULL cpu_data.
    
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43401
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43401
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43401/
[4] VulDB https://vuldb.com/cve/CVE-2026-43401
[5] https://git.kernel.org/stable/c/42738dffb7b0766a45882dff7989401d78f66f92
[6] https://git.kernel.org/stable/c/6bfda7ce56e7d14a677b7bcd6c7a5009cc29aa88
[7] https://git.kernel.org/stable/c/ab39cc4cb8ceecdc2b61747433e7237f1ac2b789

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43401", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:51.543", "lastModified": "2026-05-21T19:26:06.597", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncpufreq: intel_pstate: Fix NULL pointer dereference in update_cpu_qos_request()\n\nThe update_cpu_qos_request() function attempts to initialize the 'freq'\nvariable by dereferencing 'cpudata' before verifying if the 'policy'\nis valid.\n\nThis issue occurs on systems booted with the \"nosmt\" parameter, where\nall_cpu_data[cpu] is NULL for the SMT sibling threads. As a result,\nany call to update_qos_requests() will result in a NULL pointer\ndereference as the code will attempt to access pstate.turbo_freq using\nthe NULL cpudata pointer.\n\nAlso, pstate.turbo_freq may be updated by intel_pstate_get_hwp_cap()\nafter initializing the 'freq' variable, so it is better to defer the\n'freq' until intel_pstate_get_hwp_cap() has been called.\n\nFix this by deferring the 'freq' assignment until after the policy and\ndriver_data have been validated.\n\n[ rjw: Added one paragraph to the changelog ]"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-476"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "6.18.19", "matchCriteriaId": "4B3A7D3C-8D62-43DB-ADD2-83F0634E4C23"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.9", "matchCriteriaId": "E825E7C3-FEAC-4FD3-8A81-78D7387948C9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/42738dffb7b0766a45882dff7989401d78f66f92", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6bfda7ce56e7d14a677b7bcd6c7a5009cc29aa88", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ab39cc4cb8ceecdc2b61747433e7237f1ac2b789", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}