CVE-2026-18527 — CVSS 9.9 CRITICAL Severity | NVD Vulnerability Record

Executive Summary

The IBM Administration Runtime Expert for i (ARE) contains a remote‑code execution flaw that permits an unauthenticated attacker to assume another user’s profile and obtain full system privileges. All IBM i environments running ARE 1R1M0 are exposed, creating an immediate risk of data loss, service interruption, and regulatory breach. Decision makers must authorize emergency patch deployment, isolate vulnerable ARE instances, and activate an incident‑response plan within the next 24 hours.

Verified Facts

• CVE‑2026‑18527 identifies a privilege‑escalation vulnerability in IBM Administration Runtime Expert for i 1R1M0 — NVD.
• The flaw resides in the ARE GUI component processing, allowing an unauthenticated attacker to execute actions under another user’s authenticated profile — NVD.
• CVSS 3.1 base score is 9.9 with vector AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H — NVD.
• The vulnerability is classified as CWE‑384 (Session Fixation) — NVD.

Threat Classification

Privilege‑escalation exploit targeting IBM i application runtime environments; primary impact on financial services, manufacturing, and government sectors that rely on IBM i for core transaction processing; global exposure due to widespread IBM i deployments; exploitation status is currently theoretical with no public PoC disclosed (MEDIUM CONFIDENCE); attacker motivation is presumed to be unauthorized system control (LOW CONFIDENCE).

Threat Severity Assessment

• Exploitability: Network‑remote, low‑complexity attack vector (HIGH CONFIDENCE).
• Impact: Full system compromise with confidentiality, integrity, and availability impact (HIGH CONFIDENCE).
• Prevalence: Affects all installations of ARE 1R1M0, a widely deployed IBM i component (MEDIUM CONFIDENCE).
• CVSS score of 9.9 confirms critical severity (HIGH CONFIDENCE).

Business Impact

Successful exploitation enables attackers to modify or delete mission‑critical business data on IBM i, halting transaction processing and causing revenue loss. If compromised data includes personal or regulated information, the organization faces mandatory breach notification, regulator‑imposed fines, and potential civil litigation under GDPR, NIS2, or DORA. The breach also erodes customer trust, leading to measurable brand damage and loss of market share.

Technical Analysis

• Attack Vector: Network‑based remote call to the ARE GUI component (AV:N).
• Exploitation Chain: Unauthenticated request → GUI component processing flaw → execution of actions under another user’s session → privilege escalation to administrative level.
• Affected Component: IBM Administration Runtime Expert for i 1R1M0 (ARE GUI).
• Root Cause: Session fixation (CWE‑384) allowing attacker‑controlled session identifier to be accepted by the server.
• Authentication Requirement: None (PR:L, UI:N).
• Impact Metrics: Confidentiality, Integrity, Availability all rated High (C:H/I:H/A:H).

CVE Analysis

• CVE‑2026‑18527 — IBM Administration Runtime Expert for i 1R1M0 — CWE‑384 (Session Fixation) — Network remote (AV:N), unauthenticated (PR:L) — Patch status not disclosed in the article.

MITRE ATT&CK Mapping

• Privilege Escalation → T1068: Exploitation for Privilege Escalation — attacker exploits ARE GUI flaw to gain higher privileges.
• Initial Access → T1210: Exploitation of Remote Services — remote unauthenticated request targets the ARE service.

IOC Intelligence

No public IOCs confirmed at time of publication.

Defenders should build hunt rules around the following behavioral indicators:

• Unexpected IBM i GUI component requests originating from non‑internal IP ranges.
• Session identifiers that change without a corresponding login event.
• Creation of new administrative user accounts within minutes of a GUI request.
• Execution of privileged commands immediately following a GUI interaction.

Detection Engineering Guidance

• Collect IBM i QSYSOPR and QSYSLOG entries; filter for “ARE” or “Application Runtime Expert” strings.
• Correlate syslog events with source IPs that have no prior successful authentication on the IBM i host.
• Monitor privilege‑change audit records (e.g., *CHGUSRPRF) for rapid elevation after a GUI request.
• Enable NetFlow or Zeek logs on the network segment hosting IBM i to flag inbound TCP connections to the ARE service port (default 443) from external addresses.
• In Splunk, create a real‑time alert on: index=ibmi sourcetype=ibmi:syslog (message="*ARE*") AND src_ip!= AND action="privilege_change".

Sigma Rules

title: IBM i Application Runtime Expert Privilege Escalation
id: 9f2c3e1a-5b4d-4a9e-8c2f-1d7e6b9a4c3f
status: stable
description: Detects unauthenticated remote calls to the ARE GUI component that result in privilege escalation on IBM i systems.
logsource:
    product: ibmi
    service: syslog
detection:
    selection_gui:
        Message|contains: 'ARE GUI'
    selection_priv:
        Message|contains: 'privilege_change'
    selection_external:
        SrcIP|not|cidr: 10.0.0.0/8
    condition: selection_gui and selection_priv and selection_external
falsepositives:
    - Legitimate remote administration from approved external partners
level: high
tags:
    - attack.t1068
    - attack.t1210

Threat Hunting Queries

• Hypothesis: Unauthenticated external IPs are invoking the ARE GUI component — Source: IBM i syslog (Message field contains “ARE GUI” and SrcIP not in internal CIDR).
• Hypothesis: Session IDs are reused across different user contexts — Source: IBM i audit logs (SessionID field changes without corresponding login events).
• Hypothesis: New admin accounts appear shortly after an ARE request — Source: IBM i user management logs (EventType=CreateUser, Privilege=ADMIN, Timestamp within 5 min of ARE request).
• Hypothesis: Privileged commands execute from IPs with no prior authentication — Source: Command audit logs (Command=*, SrcIP not in internal CIDR, AuthStatus=Unauthenticated).
• Hypothesis: Network traffic to the ARE service port originates from external subnets — Source: Zeek/NetFlow (dest_port=443, service=ARE, src_ip not in internal CIDR).

SOC Analyst Playbook

• P0 – Verify alert: Check IBM i syslog for “ARE GUI” entries from external IPs; confirm no legitimate remote admin contract exists.
• P0 – Contain: Block source IP at perimeter firewall; disable ARE GUI service on affected host.
• P1 – Investigate: Query IBM i audit logs for privilege_change events linked to the same source IP; capture session IDs and timestamps.
• P1 – Eradicate: Apply IBM‑issued patch (if available) or revert to a known‑good configuration; reset passwords for all accounts with elevated privileges.
• P2 – Recover: Restore affected services from clean backups; conduct integrity verification of critical data files.
• P2 – Post‑incident: Update run‑books with detection signatures; produce incident report for management.

Executive Decision Matrix

🔗 Related Intelligence Reports

• Related topic: CVE-2026-19286 — CVSS 9.8 CRITICAL Severity | NVD Vulnerability Record
• Related topic: CVE-2026-19295 — CVSS 9.9 CRITICAL Severity | NVD Vulnerability Record
• Related topic: CVE-2026-3627 — CVSS 9.1 CRITICAL Severity | NVD Vulnerability Record
• Related topic: CVE-2026-76581 — CVSS 9.8 CRITICAL Severity | NVD Vulnerability Record
• Related topic: CVE-2026-82244 — CVSS 9.1 CRITICAL Severity | NVD Vulnerability Record