MEDIUM CVSS 5.5
Published: 2026-05-06

CVE-2026-43087

linux linux_kernel Security Advisory (CVE-2026-43087)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-43087 impacting linux linux_kernel. Evaluated with CVSS Base Score of 5.5 (MEDIUM).

Original NVD Description

Source: NIST NVD
In the Linux kernel, the following vulnerability has been resolved: pinctrl: mcp23s08: Disable all pin interrupts during probe A chip being probed may have the interrupt-on-change feature enabled on some of its pins, for example after a reboot. This can cause the chip to generate interrupts for pins that don't have a registered nested handler, which leads to a kernel crash such as below: [ 7.928897] Unable to handle kernel read from unreadable memory at virtual address 00000000000000ac [ 7.932314] Mem abort info: [ 7.935081] ESR = 0x0000000096000004 [ 7.938808] EC = 0x25: DABT (current EL), IL = 32 bits [ 7.944094] SET = 0, FnV = 0 [ 7.947127] EA = 0, S1PTW = 0 [ 7.950247] FSC = 0x04: level 0 translation fault [ 7.955101] Data abort info: [ 7.957961] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 [ 7.963421] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 7.968447] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 7.973734] user pgtable: 4k pages, 48-bit VAs, pgdp=00000000089b7000 [ 7.980148] [00000000000000ac] pgd=0000000000000000, p4d=0000000000000000 [ 7.986913] Internal error: Oops: 0000000096000004 [#1] SMP [ 7.992545] Modules linked in: [ 8.073678] CPU: 0 UID: 0 PID: 81 Comm: irq/18-4-0025 Not tainted 7.0.0-rc6-gd2b5a1f931c8-dirty #199 [ 8.073689] Hardware name: Khadas VIM3 (DT) [ 8.073692] pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 8.094639] pc : _raw_spin_lock_irq+0x40/0x80 [ 8.098970] lr : handle_nested_irq+0x2c/0x168 [ 8.098979] sp : ffff800082b2bd20 [ 8.106599] x29: ffff800082b2bd20 x28: ffff800080107920 x27: ffff800080104d88 [ 8.106611] x26: ffff000003298080 x25: 0000000000000001 x24: 000000000000ff00 [ 8.113707] x23: 0000000000000001 x22: 0000000000000000 x21: 000000000000000e [ 8.120850] x20: 0000000000000000 x19: 00000000000000ac x18: 0000000000000000 [ 8.135046] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 [ 8.135062] x14: ffff800081567ea8 x13: ffffffffffffffff x12: 0000000000000000 [ 8.135070] x11: 00000000000000c0 x10: 0000000000000b60 x9 : ffff800080109e0c [ 8.135078] x8 : 1fffe0000069dbc1 x7 : 0000000000000001 x6 : ffff0000034ede00 [ 8.135086] x5 : 0000000000000000 x4 : ffff0000034ede08 x3 : 0000000000000001 [ 8.163460] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 00000000000000ac [ 8.170560] Call trace: [ 8.180094] _raw_spin_lock_irq+0x40/0x80 (P) [ 8.184443] mcp23s08_irq+0x248/0x358 [ 8.184462] irq_thread_fn+0x34/0xb8 [ 8.184470] irq_thread+0x1a4/0x310 [ 8.195093] kthread+0x13c/0x150 [ 8.198309] ret_from_fork+0x10/0x20 [ 8.201850] Code: d65f03c0 d2800002 52800023 f9800011 (885ffc01) [ 8.207931] ---[ end trace 0000000000000000 ]--- This issue has always been present, but has been latent until commit "f9f4fda15e72" ("pinctrl: mcp23s08: init reg_defaults from HW at probe and switch cache type"), which correctly removed reg_defaults from the regmap and as a side effect changed the behavior of the interrupt handler so that the real value of the MCP_GPINTEN register is now being read from the chip instead of using a bogus 0 default value; a non-zero value for this register can trigger the invocation of a nested handler which may not exist (yet). Fix this issue by disabling all pin interrupts during initialization.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Local (AV:L)
Requires local system execution permissions
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
Low (PR:L)
Standard user access required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product linux / linux_kernel
Affected Versions *
Weakness Enumeration NVD-CWE-noinfo

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-43087 impacting linux linux_kernel.

⚡ Nuclei Detection Template (YAML) cve-2026-43087.yaml 
id: cve-2026-43087

info:
  name: linux linux_kernel - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-43087 affecting linux linux_kernel.
    Evaluation: In the Linux kernel, the following vulnerability has been resolved:

pinctrl: mcp23s08: Disable all pin interrupts during probe

A chip being probed m...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-43087
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 5.5
    cve-id: CVE-2026-43087
    cwe-id: NVD-CWE-noinfo
  tags: cve,cve-2026-43087,linux,linux_kernel,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "linux_kernel"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-43087.py 
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-43087
# Target: linux linux_kernel | CVSS: 5.5 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-43087 (linux linux_kernel)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against linux linux_kernel scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-43087.sh 
# Recommended Remediation & Patching Commands for CVE-2026-43087
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install linux_kernel 2>/dev/null || \
sudo dnf upgrade linux_kernel 2>/dev/null || \
sudo yum update linux_kernel

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i linux_kernel 2>/dev/null || rpm -qa | grep -i linux_kernel

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-43087 in linux linux_kernel?

Review vendor-specific security notices and update linux linux_kernel packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-43087?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-43087?

CVE-2026-43087 is classified with a CVSS 3.1 Base Score of 5.5 (MEDIUM). Check the metric breakdown above for attack vector requirements.

🕸️ Spider Mesh Intelligence Graph (Connected Advisories)

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Risk Snapshot
5.5
MEDIUM SEVERITY
CVE ID CVE-2026-43087
Weakness NVD-CWE-noinfo
Vendor linux
Product linux_kernel
Published 2026-05-06
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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