CVE-2026-18065 Overview
CVE-2026-18065 is an authentication weakness in IBM i Navigator that allows a remote unauthenticated attacker to access sensitive information by bypassing session IP binding. The flaw affects IBM i versions 7.6, 7.5, 7.4, and 7.3. It is categorized under [CWE-290] Authentication Bypass by Spoofing, where session validation controls fail to properly tie an active session to its originating client IP address. Successful exploitation exposes information handled through the Navigator for i web interface without requiring credentials or user interaction.
Critical Impact
Remote unauthenticated attackers can bypass IP-based session binding in Navigator for i and read sensitive information exposed by an active administrator session.
Affected Products
- IBM i 7.6
- IBM i 7.5
- IBM i 7.4
- IBM i 7.3
Discovery Timeline
- 2026-09-14 - CVE-2026-18065 published to NVD
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-18065
Vulnerability Analysis
Navigator for i is the browser-based administration console shipped with IBM i. It authenticates users and issues a session identifier that should be bound to the originating client IP address. CVE-2026-18065 breaks that binding. An attacker who obtains or replays a valid session artifact can present it from a different network address and still be treated as an authorized session by the server.
The issue falls under [CWE-290] Authentication Bypass by Spoofing. Because the vulnerability is reachable over the network, requires no privileges, and needs no user interaction, exploitation attempts can be fully automated against exposed Navigator endpoints. The impact is limited to confidentiality; integrity and availability of the host system are not affected.
Root Cause
The root cause is incomplete enforcement of the session-to-client-IP association inside Navigator for i. Session validation logic accepts a session token without confirming that the request originates from the IP address recorded at session creation, letting an attacker substitute their own address while presenting a captured or otherwise obtained session artifact.
Attack Vector
Exploitation occurs over the network against a reachable Navigator for i instance. An attacker who acquires a session identifier — through network observation, log exposure, browser artifacts, or a co-resident foothold — can replay it from an arbitrary source address. The server processes the request as if it came from the legitimate session owner and returns sensitive information exposed by the Navigator interface.
No verified proof-of-concept code is public. See the IBM Support Article for vendor technical details.
Detection Methods for CVE-2026-18065
Indicators of Compromise
- The same Navigator for i session identifier used from two or more distinct source IP addresses within a short time window.
- Navigator for i requests where the request source IP does not match the IP recorded at session establishment.
- Access to sensitive Navigator pages from geographic regions or ASNs that do not match the authenticated administrator's baseline.
Detection Strategies
- Correlate Navigator for i HTTP access logs with authentication events to identify session IDs presented from mismatched client addresses.
- Alert on concurrent active sessions for the same IBM i user account originating from different networks.
- Baseline administrator access patterns to Navigator for i and flag deviations in source IP, user agent, or time of day.
Monitoring Recommendations
- Forward Navigator for i and HTTP server logs to a centralized analytics platform for retention and correlation.
- Monitor egress and ingress paths to the Navigator listening port for anomalous access from untrusted networks.
- Track failed and successful administrative actions performed in Navigator for i for post-incident forensics.
How to Mitigate CVE-2026-18065
Immediate Actions Required
- Restrict network access to Navigator for i so that only trusted management networks can reach the service.
- Apply the IBM-provided fix for IBM i 7.6, 7.5, 7.4, and 7.3 as documented in the vendor advisory.
- Invalidate existing Navigator for i sessions and require administrators to re-authenticate after patching.
Patch Information
IBM has published remediation guidance in the IBM Support Article covering IBM i 7.6, 7.5, 7.4, and 7.3. Administrators should apply the referenced PTFs and confirm Navigator for i has been restarted so the updated session validation logic is loaded.
Workarounds
- Place Navigator for i behind a VPN or jump host to prevent direct exposure to untrusted networks.
- Enforce firewall rules that allow Navigator for i traffic only from a defined list of administrator source addresses.
- Reduce Navigator for i session timeout values to shrink the window in which a captured session identifier remains valid.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
