CVE-2024-51476: IBM Concert Software Auth Bypass Flaw

CVE-2024-51476 Overview

CVE-2024-51476 affects IBM Concert Software version 1.0.5. The product uses an inadequate account lockout setting, which allows remote attackers to perform brute-force attacks against account credentials. The weakness is classified under [CWE-307] (Improper Restriction of Excessive Authentication Attempts).

An unauthenticated attacker can repeatedly submit authentication requests over the network without triggering a lockout. Successful credential guessing leads to account compromise and unauthorized access to data managed by IBM Concert.

Critical Impact

Remote, unauthenticated attackers can brute-force valid credentials against IBM Concert Software 1.0.5, leading to account takeover and exposure of confidential information.

Affected Products

• IBM Concert Software 1.0.5
• Deployments running on Linux kernel hosts
• Environments exposing the Concert authentication interface to untrusted networks

Discovery Timeline

• 2025-03-06 - CVE-2024-51476 published to the National Vulnerability Database
• 2025-07-16 - Record last modified in NVD

Technical Details for CVE-2024-51476

Vulnerability Analysis

IBM Concert Software 1.0.5 does not enforce a sufficient account lockout policy on its authentication endpoint. Authentication requests are accepted at a rate and volume that permits automated credential guessing. The flaw maps to [CWE-307], Improper Restriction of Excessive Authentication Attempts.

The weakness is reachable over the network without prior authentication or user interaction. Attackers only need network connectivity to the Concert authentication interface and a target username. Confidentiality is the primary impact, since successful guessing yields valid session credentials.

The EPSS probability is 0.094% with a percentile of 26.178, reflecting low observed exploitation activity to date. No public proof-of-concept or exploit code is currently available, and CISA has not added the issue to the Known Exploited Vulnerabilities catalog.

Root Cause

The root cause is missing or misconfigured authentication throttling. Concert Software does not lock accounts, slow responses, or otherwise rate-limit failed login attempts at a threshold low enough to defeat automated guessing tools.

Without a lockout counter, exponential backoff, or CAPTCHA challenge, an attacker can submit thousands of password guesses per account. Common weak or reused passwords are recovered quickly through dictionary attacks.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker scripts authentication requests against the Concert login endpoint using a username list and a password dictionary. The attacker iterates until valid credentials produce a successful authentication response.

Once credentials are recovered, the attacker logs in as the compromised user and accesses application data and functionality at that user's privilege level. Credential stuffing using credentials leaked from unrelated breaches is also feasible against this endpoint.

No public exploitation code is available. The vulnerability is described in prose only; see the IBM Support Page for vendor guidance.

Detection Methods for CVE-2024-51476

Indicators of Compromise

• High volumes of failed authentication events against IBM Concert accounts from a single source or a distributed set of sources
• Successful logins immediately following long sequences of failed attempts for the same account
• Authentication attempts spanning many usernames from a single client within a short window, indicating credential stuffing
• Logins from geolocations or ASNs that do not match the user's normal access pattern

Detection Strategies

• Aggregate Concert authentication logs and alert on failed-login thresholds per account and per source IP over rolling time windows
• Correlate failed-then-successful login sequences to identify potentially successful brute-force outcomes
• Baseline normal login volumes per user and flag statistical anomalies in attempt frequency or source diversity

Monitoring Recommendations

• Forward Concert authentication and audit logs to a centralized SIEM or data lake for retention and correlation
• Monitor reverse proxies, load balancers, and WAFs in front of Concert for repeated POSTs to the login URL
• Track session creation events and review sessions originating from new IP addresses or user agents

How to Mitigate CVE-2024-51476

Immediate Actions Required

• Apply the fix referenced in the IBM Support Page for IBM Concert Software
• Restrict network exposure of the Concert authentication interface to trusted networks and VPN users only
• Force a password reset for all Concert accounts and require strong, unique passwords
• Enable multi-factor authentication where supported to neutralize single-factor credential guessing

Patch Information

IBM has published remediation guidance at the IBM Support Page. Administrators running IBM Concert Software 1.0.5 should follow the vendor advisory to apply the corrective update or configuration change that introduces an adequate account lockout policy.

Workarounds

• Place Concert behind a reverse proxy or WAF that enforces rate limiting and IP-based blocking after repeated authentication failures
• Restrict access to the login endpoint using network ACLs, firewall rules, or zero-trust access policies
• Implement external IdP-based authentication with lockout and MFA controls if the application supports federated login
• Audit and disable unused or dormant Concert accounts to reduce the credential attack surface

# Example: rate-limit authentication attempts at an NGINX reverse proxy
# Limits each client IP to 5 requests per minute to the Concert login endpoint
http {
    limit_req_zone $binary_remote_addr zone=concert_login:10m rate=5r/m;

    server {
        location /login {
            limit_req zone=concert_login burst=5 nodelay;
            proxy_pass http://concert_backend;
        }
    }
}