HIGH CVSS 7.8
Published: 2026-09-11

CVE-2026-89581

Software Component Security Advisory (CVE-2026-89581)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-89581 impacting Software Component. Evaluated with CVSS Base Score of 7.8 (HIGH).

Original NVD Description

Source: NIST NVD
In the Linux kernel, the following vulnerability has been resolved: bpf, x86: Fix per-CPU address resolution into an extended register The destination of the per-CPU address MOV is encoded in ModRM.reg, which is extended by REX.R, but the REX prefix is built with add_1mod(), which sets REX.B. REX.B extends ModRM.rm and SIB.base, and this instruction addresses memory as disp32 with no base, so the bit has no effect at all and the high register bit is simply lost. Every is_ereg() destination therefore resolves to the wrong register, picking whichever one shares the low three bits: R5 -> RAX R7 -> RBP R8 -> RSI R9 -> RDI With BPF_REG_5, whose reg2hex is 0, the emitted 65 49 03 04 25 <off> add %gs:<off>,%rax adds the per-CPU offset to RAX rather than R8. The destination keeps the unadjusted address and RAX is clobbered, so the program goes on to dereference a pointer that was never made per-CPU: BUG: unable to handle page fault for address: 0000607e386a8894 RIP: bpf_prog_707837aafd2aa9ae_update_percpu_data+0x93/0xc9 Call Trace: __bpf_prog_test_run_raw_tp+0x2dc/0x7d0 __flush_smp_call_function_queue+0x1e9/0xc80 Kernel panic - not syncing: Fatal exception in interrupt R5 is the mildest of the four, aliasing a scratch register and faulting at the store. R7 aliases RBP and would corrupt the frame pointer, R8 and R9 alias the argument registers. Use add_2mod() so the register goes through REX.R, matching how add_2reg() places it in ModRM.reg and how emit_priv_frame_ptr() hardcodes 0x4c for the same instruction with R9. Encodings for the non-extended registers are unchanged. Problem showed up when trying to resurrect BPF_GCC CI (selftests built with BPF_GCC). This has gone unnoticed because clang reloads the address into R1 before each per-CPU access, so the destination is never an extended register. GCC keeps several per-CPU addresses live at once, and test_progs-bpf_gcc panics the kernel in global_percpu_data/init, where the address of a .percpu variable ends up in R5.

📊 CVSS v3.1 Metric Breakdown

🎯 Affected Versions Matrix

Affected Product Generic/Unknown / Software Component
Affected Versions Unspecified
Weakness Enumeration CWE-Not-Specified

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-2026-89581 impacting Software Component.

⚡ Nuclei Detection Template (YAML) cve-2026-89581.yaml
id: cve-2026-89581

info:
  name: Software Component - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-89581 affecting Software Component.
    Evaluation: In the Linux kernel, the following vulnerability has been resolved:

bpf, x86: Fix per-CPU address resolution into an extended register

The destinati...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-89581
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 7.8
    cve-id: CVE-2026-89581
    cwe-id: CWE-Not-Specified
  tags: cve,cve-2026-89581,generic,software,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "Server"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-89581.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-89581
# Target: Software Component | CVSS: 7.8 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-89581 (Software Component)...")
    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 Software Component scope (Unspecified).")
        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-2026-89581.sh
# Recommended Remediation & Patching Commands for CVE-2026-89581
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install software 2>/dev/null || \
sudo dnf upgrade software 2>/dev/null || \
sudo yum update software

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

# 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.
Technical Analysis
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-89581 in Software Component?

Review vendor-specific security notices and update Software Component 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-2026-89581?

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-2026-89581?

CVE-2026-89581 is classified with a CVSS 3.1 Base Score of 7.8 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.8
HIGH SEVERITY
CVE ID CVE-2026-89581
Weakness CWE-Not-Specified
Vendor Generic/Unknown
Product Software Component
Published 2026-09-11
Vector N/A