CVE-2024-31878: IBM i Service Tools Server User Enumeration

CVE-2024-31878 Overview

CVE-2024-31878 affects the IBM i Service Tools Server (SST) across versions 7.2, 7.3, 7.4, and 7.5. The vulnerability allows a remote, unauthenticated attacker to enumerate valid SST usernames by observing differences in server responses. Tracked under IBM X-Force ID 287538, the flaw is categorized as an information disclosure issue [CWE-203: Observable Discrepancy]. Attackers can use enumerated SST accounts as targets for password guessing, credential stuffing, or social engineering campaigns aimed at IBM i administrative interfaces.

Critical Impact
Remote attackers can identify valid SST user accounts without authentication, providing reconnaissance data that enables targeted attacks against IBM i system administration surfaces.

Affected Products

IBM i 7.2
IBM i 7.3
IBM i 7.4 and IBM i 7.5

Discovery Timeline

2024-06-07 - CVE-2024-31878 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-31878

Vulnerability Analysis

The Service Tools Server (SST) on IBM i handles low-level system service functions, including hardware service, disk configuration, and privileged user management. SST maintains its own user directory separate from standard IBM i user profiles. CVE-2024-31878 arises from the SST authentication flow producing observable differences in behavior when presented with a valid versus invalid SST user identifier. An attacker interacting with SST across the network can distinguish these responses and compile a list of legitimate accounts.

While the vulnerability itself does not grant access or leak credentials, SST accounts are high-value targets. Compromise of an SST account can lead to disk unit reconfiguration, license internal code operations, and recovery of privileged IBM i functions. Enumerated identities materially reduce the cost of subsequent brute-force or targeted phishing operations against IBM i operators.

Root Cause

The root cause is an observable discrepancy [CWE-203] in the SST authentication handler. The server returns response characteristics — timing, message content, or state transitions — that differ based on whether the supplied SST user name exists. This divergence exposes the existence of accounts to any network client that can reach the SST listener.

Attack Vector

Exploitation requires only network reachability to the SST service. No authentication or user interaction is needed. An attacker scripts requests iterating through candidate user names and classifies responses to build a roster of valid SST accounts. Because SST is typically exposed to internal management networks, hostile insiders or attackers who have gained a foothold on a management VLAN are the most likely threat actors.

No verified proof-of-concept code is publicly available for CVE-2024-31878. See the IBM X-Force Vulnerability #287538 entry for the vendor technical summary.

Detection Methods for CVE-2024-31878

Indicators of Compromise

Bursts of SST authentication requests from a single source enumerating sequential or dictionary-based user names.
Repeated failed SST logon audit journal entries (QAUDJRN type PW) originating from unexpected IP addresses.
Unusual scanning traffic directed at IBM i service ports on the management network.

Detection Strategies

Enable and review the IBM i security audit journal (QAUDJRN) with QAUDLVL including *AUTFAIL to capture SST authentication failures.
Correlate SST logon failures against network flow logs to identify enumeration patterns from a single source across many user names.
Alert on any SST authentication traffic sourced from outside authorized administrative subnets.

Monitoring Recommendations

Forward IBM i audit journal events to a centralized analytics platform for baseline and anomaly detection.
Track the rate of distinct SST user names attempted per source address over short time windows.
Monitor for SST access attempts outside of scheduled administrative maintenance windows.

How to Mitigate CVE-2024-31878

Immediate Actions Required

Apply the IBM PTFs referenced in the vendor advisory at IBM Support page 7156725 for each affected release of IBM i 7.2, 7.3, 7.4, and 7.5.
Restrict network access to the Service Tools Server to a dedicated administrative subnet using firewall or IBM i exit-program controls.
Review the SST user list with STRSST and remove or disable unused SST profiles to reduce the enumeration target set.

Patch Information

IBM has published fixes through the support portal. Consult IBM Support Page Node #7156725 for the specific PTF group and firmware level required for each IBM i release. Cross-reference the IBM X-Force Vulnerability #287538 entry for remediation metadata.

Workarounds

Place the IBM i management interfaces behind a jump host and require VPN authentication before SST is reachable.
Enforce strong, unique SST passwords and rotate them regularly to reduce the value of enumerated account names.
Use non-obvious SST user names rather than predictable defaults to increase the cost of dictionary-based enumeration.

bash

# Example: review SST-related audit failures on IBM i
# Run from a 5250 session with sufficient authority
DSPAUDJRNE ENTTYP(PW) JRN(QAUDJRN) OUTPUT(*PRINT)

# Restrict SST network reachability via a firewall (example iptables rule
# applied on an upstream Linux gateway protecting the IBM i management VLAN)
iptables -A FORWARD -p tcp -d <ibmi_mgmt_ip> --dport 3000 \
  -s <admin_subnet>/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <ibmi_mgmt_ip> --dport 3000 -j DROP