CVE-2025-42600: Meon KYC Auth Bypass Vulnerability

CVE-2025-42600 Overview

CVE-2025-42600 is a high-severity authentication weakness affecting Meon KYC solutions. The vulnerability exists because certain login API endpoints fail to restrict the number of incorrect One-Time Password (OTP) attempts. A remote, unauthenticated attacker can iterate through the OTP keyspace and gain unauthorized access to other users' accounts. The flaw maps to CWE-307: Improper Restriction of Excessive Authentication Attempts and was published by CERT-In in advisory CIVN-2025-0082.

Critical Impact
Successful brute-force of OTP values grants attackers unauthorized access to victim accounts on Meon KYC platforms, exposing sensitive identity verification data.

Affected Products

Meon KYC solutions (login API endpoints handling OTP validation)
Refer to CERT-In Vulnerability Note CIVN-2025-0082 for the vendor-provided list of impacted versions

Discovery Timeline

2025-04-23 - CVE-2025-42600 published to NVD
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-42600

Vulnerability Analysis

The vulnerability resides in the OTP validation logic of Meon KYC's login workflow. Specific API endpoints accept OTP submissions without enforcing rate limits, lockouts, or attempt counters. An attacker who knows or guesses a target's identifier (such as a phone number or email) can submit the OTP verification request repeatedly until the correct value is found.

Because OTPs are typically short numeric codes (commonly 4-6 digits), the search space is small enough to enumerate within seconds when no throttling is in place. The EPSS score of 1.14% (78th percentile) reflects elevated probability of exploitation activity relative to most CVEs.

Root Cause

The root cause is a missing security control: the OTP verification endpoint does not enforce an upper bound on the number of invalid attempts per session, user, or source IP. There is no exponential backoff, no CAPTCHA challenge, and no account lockout after repeated failures. This is a textbook instance of CWE-307.

Attack Vector

The attack is performed remotely over the network without authentication or user interaction. An attacker scripts repeated HTTP requests against the vulnerable login API, varying the OTP value on each request. Once the server returns a success response, the attacker obtains a valid session for the target account. Refer to the CERT-In advisory for technical specifics on the affected endpoints.

Detection Methods for CVE-2025-42600

Indicators of Compromise

High volumes of OTP validation requests from a single source IP, ASN, or user agent within a short time window
Repeated failed OTP attempts followed by a successful login for the same user identifier
Successful logins from geolocations or devices inconsistent with the user's historical access patterns
Anomalous spikes in 4xx responses on OTP verification endpoints followed by a 2xx success

Detection Strategies

Aggregate authentication logs by user identifier and source IP, alerting on thresholds of failed OTP attempts (for example, more than 10 failures per minute)
Correlate failed OTP responses with subsequent successful authentication events on the same account
Apply behavioral analytics to flag automated request patterns such as fixed inter-request timing or non-browser user agents hitting login APIs

Monitoring Recommendations

Forward Meon KYC application and web server logs to a centralized SIEM for retention and correlation
Monitor WAF and API gateway telemetry for burst traffic to OTP endpoints
Track session creation events tied to KYC accounts and alert on anomalous post-login activity such as profile changes or data exports

How to Mitigate CVE-2025-42600

Immediate Actions Required

Apply the vendor patch or hotfix referenced in CERT-In Vulnerability Note CIVN-2025-0082 as soon as it is available
Contact Meon support to confirm the fixed version and required configuration changes
Review authentication logs for the last 90 days for evidence of brute-force activity against OTP endpoints
Force password and session resets for any accounts showing suspicious login patterns

Patch Information

Meon has been notified through CERT-In. Customers should consult the CERT-In advisory and engage Meon directly to obtain the remediated build. No public patch identifier is included in the NVD record at this time.

Workarounds

Implement rate limiting at the WAF or API gateway, restricting OTP verification requests per source IP and per user identifier
Enforce account lockout or temporary throttling after a small number of consecutive failed OTP attempts (typically 3-5)
Reduce OTP validity windows and increase OTP length or entropy to shrink the brute-force window
Add CAPTCHA or device fingerprinting challenges on the OTP verification endpoint to block automated tooling

bash

# Example NGINX rate-limit snippet for OTP verification endpoint
limit_req_zone $binary_remote_addr zone=otp_zone:10m rate=5r/m;

location /api/login/verify-otp {
    limit_req zone=otp_zone burst=3 nodelay;
    proxy_pass http://meon_backend;
}