CVE-2026-18531: IBM Maximo Session Tampering Vulnerability

CVE-2026-18531 Overview

CVE-2026-18531 affects IBM Maximo Application Suite versions 9.0, 9.1, and 9.2. The vulnerability stems from the use of a weak Hash-based Message Authentication Code (HMAC) session signing secret. A remote attacker can tamper with session data without authentication or user interaction. The weakness is categorized under [CWE-330: Use of Insufficiently Random Values]. Successful exploitation compromises the integrity of session tokens, enabling forgery or modification of signed session content processed by the application.

Critical Impact
Remote attackers can tamper with signed session data over the network without credentials, undermining the integrity guarantees that HMAC session signing is intended to provide.

Affected Products

IBM Maximo Application Suite 9.0
IBM Maximo Application Suite 9.1
IBM Maximo Application Suite 9.2

Discovery Timeline

2026-08-05 - CVE-2026-18531 published to the National Vulnerability Database (NVD)
2026-08-05 - Last updated in NVD database

Technical Details for CVE-2026-18531

Vulnerability Analysis

IBM Maximo Application Suite uses HMAC to sign session data so the server can verify that session tokens have not been altered by the client. The security of HMAC depends entirely on the secrecy and unpredictability of the signing key. In the affected releases, the session signing secret is weak, meaning it can be guessed, brute-forced, or otherwise recovered by an attacker without privileged access. Once the secret is known, an attacker can produce valid HMAC signatures for arbitrary session payloads. This allows tampering with fields inside the session, such as identifiers, role indicators, or workflow state, while still passing server-side signature verification. The flaw does not require prior authentication and is exploitable over the network against exposed Maximo endpoints.

Root Cause

The root cause is the selection of an insufficiently random or otherwise weak value as the HMAC session signing secret. HMAC constructions remain cryptographically sound only when the key is drawn from a large keyspace using a cryptographically secure random source. A weak default, low-entropy secret, or predictable derivation lets attackers recover the key offline, defeating signature verification.

Attack Vector

An unauthenticated remote attacker interacts with the Maximo Application Suite over the network. The attacker obtains one or more signed session tokens issued by the application, then works to recover the signing secret through brute force or dictionary attack against the HMAC output. With the recovered secret, the attacker crafts modified session payloads, computes a valid HMAC, and submits the forged session to the server. The server accepts the signature as authentic and processes the tampered session data. No user interaction is required, and no privileges are needed to initiate the attack. Verified proof-of-concept code is not publicly listed for this CVE in the referenced advisory.

Detection Methods for CVE-2026-18531

Indicators of Compromise

Session tokens presented to the server whose decoded payload contains unexpected identifier, role, or tenant values that do not match issuance records.
Repeated authentication or session validation requests from a single source that iterate through candidate session values.
Access to authenticated Maximo functionality from source IPs or user agents that never completed a valid login flow.
Server-side session decode events succeeding for users whose accounts show no corresponding login event in identity logs.

Detection Strategies

Correlate Maximo application logs with authentication logs to flag session use that lacks a matching successful login event.
Monitor for anomalous rates of session validation failures followed by successes from the same client, indicating signature guessing attempts.
Inspect signed session payloads for values that violate application invariants, such as elevated roles for accounts that never held them.

Monitoring Recommendations

Enable verbose logging on Maximo authentication and session subsystems and forward logs to a central analytics platform.
Alert on session decoding for privileged accounts originating from previously unseen network locations.
Track the ratio of session validation failures to successes over time and investigate sharp deviations.

How to Mitigate CVE-2026-18531

Immediate Actions Required

Apply the fix referenced in the IBM Support Page for Maximo Application Suite 9.0, 9.1, and 9.2.
Rotate the HMAC session signing secret to a high-entropy value generated by a cryptographically secure random source after patching.
Invalidate all existing sessions so that tokens signed with the previous weak secret can no longer be accepted.
Restrict network exposure of Maximo Application Suite management and session endpoints to trusted networks where feasible.

Patch Information

IBM has published remediation guidance for CVE-2026-18531 on the IBM Support Page. Administrators should review the advisory for the specific fix pack or interim fix applicable to their Maximo Application Suite 9.0, 9.1, or 9.2 deployment and apply it in accordance with IBM's instructions.

Workarounds

Place Maximo Application Suite behind a reverse proxy or web application firewall that enforces authentication before session tokens are processed.
Reduce session lifetimes so that any tampered session has a smaller window of validity while the patch is being scheduled.
Limit session-bearing endpoints to authenticated network segments using network access controls until patching completes.

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# Configuration example not available - refer to the IBM Support Page
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