CVE-2025-42603: Meon KYC Information Disclosure Flaw

CVE-2025-42603 Overview

CVE-2025-42603 affects Meon KYC solutions and results from cleartext transmission of sensitive data within API response payloads [CWE-319]. Certain API endpoints return unencrypted personally identifiable information in responses accessible to authenticated users. An authenticated remote attacker can intercept these responses to obtain sensitive data belonging to other users. Successful exploitation enables account impersonation and unauthorized access to victim accounts. The Indian Computer Emergency Response Team (CERT-In) published advisory CIVN-2025-0082 describing the issue.

Critical Impact
Authenticated remote attackers can harvest sensitive user data transmitted in plain text and impersonate other users to gain unauthorized account access.

Affected Products

Meon KYC solutions (vendor advisory CIVN-2025-0082)
Specific affected versions not enumerated in the public advisory
Customer deployments consuming the vulnerable API endpoints

Discovery Timeline

2025-04-23 - CVE-2025-42603 published to the National Vulnerability Database
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-42603

Vulnerability Analysis

The vulnerability stems from improper handling of sensitive data in API response payloads. The affected Meon KYC endpoints return sensitive user information without encryption or tokenization at the application layer. Any authenticated user who can reach these endpoints, or any party able to observe the response traffic, can extract data belonging to other users.

Know Your Customer (KYC) platforms typically process government identifiers, financial details, biometric metadata, and contact records. Exposing this data in cleartext within API responses creates a direct path to identity theft and account takeover. Attackers reusing harvested credentials or identity attributes can pass downstream authentication checks and impersonate legitimate users.

The issue is classified under [CWE-319] Cleartext Transmission of Sensitive Information. The attack requires network access to the API but no user interaction. The Exploit Prediction Scoring System assigns this CVE a probability score indicating moderate likelihood of exploitation activity within the next 30 days.

Root Cause

The root cause is the application returning sensitive fields in API responses without applying field-level encryption, masking, or authorization filtering. The endpoints fail to validate that the requesting principal is authorized for the data returned and transmit the payload in cleartext at the application layer.

Attack Vector

An authenticated attacker issues requests to vulnerable API endpoints and observes the responses. The responses contain unencrypted records associated with other users. The attacker captures identifiers and KYC attributes, then replays them to impersonate the targeted user across dependent services.

No verified proof-of-concept code is publicly available. Refer to the CERT-In Advisory CIVN-2025-0082 for vendor-supplied technical details.

Detection Methods for CVE-2025-42603

Indicators of Compromise

Unusual volumes of authenticated API requests to KYC endpoints from a single session or IP address.
API responses returning records for user identifiers that do not match the authenticated principal.
Sequential or enumerated identifier patterns in request parameters targeting user-specific endpoints.
Outbound transfers of large JSON or XML payloads from API gateways to external destinations.

Detection Strategies

Inspect API gateway logs for response payloads containing sensitive fields such as identifiers, dates of birth, or document numbers.
Compare the authenticated user identity in the session against user identifiers present in the response body.
Deploy data loss prevention rules on egress traffic to flag KYC field patterns leaving the application boundary.

Monitoring Recommendations

Enable verbose access logging on all KYC API endpoints and forward logs to a central SIEM for correlation.
Alert on accounts retrieving records at rates exceeding normal business workflows.
Monitor for anomalous geographic or device fingerprints associated with successful authentication followed by bulk API queries.

How to Mitigate CVE-2025-42603

Immediate Actions Required

Contact Meon to obtain the patched build addressing CIVN-2025-0082 and schedule deployment.
Audit API responses for sensitive fields and remove any data not required by the calling client.
Enforce object-level authorization so each request returns only data tied to the authenticated principal.
Rotate authentication tokens and force password resets for accounts showing anomalous KYC data access.

Patch Information

Apply the fixed release from Meon as referenced in CERT-In Advisory CIVN-2025-0082. Public NVD entries do not list specific fixed version numbers. Customers should contact the vendor directly to confirm the patched build applicable to their deployment.

Workarounds

Restrict access to vulnerable API endpoints through network segmentation and allowlisted client identities until a patch is applied.
Add a reverse proxy or API gateway policy that masks or strips sensitive fields from outbound responses.
Enforce TLS 1.2 or higher with strict certificate validation across all client-to-API communication paths.

bash

# Example NGINX response filtering to redact sensitive fields
location /api/kyc/ {
    proxy_pass https://backend.internal/;
    sub_filter_types application/json;
    sub_filter '"aadhaar":"[^"]*"' '"aadhaar":"REDACTED"';
    sub_filter '"pan":"[^"]*"'     '"pan":"REDACTED"';
    sub_filter_once off;
}