CVE-2025-42605 is an authorization bypass vulnerability identified in Meon Bidding Solutions version 1.2. The root cause of this vulnerability lies in improper authorization controls on certain API endpoints responsible for initiating, modifying, or canceling bidding operations. Specifically, the flaw allows an authenticated remote attacker to manipulate a user-controlled parameter within the API request body, which is used as a key to authorize actions. Due to insufficient validation of this parameter, the attacker can bypass authorization checks and gain unauthorized access to other users' accounts. This unauthorized access enables the attacker to perform actions such as modifying or canceling bids associated with other users, potentially leading to data integrity issues and unauthorized manipulation of bidding data. The vulnerability is classified under CWE-639, which pertains to authorization bypass through user-controlled keys. Exploitation does not require privilege escalation beyond authentication, but does require the attacker to be authenticated. There are no known exploits in the wild at this time, and no patches have been publicly released. The vulnerability was reserved and published in April 2025, with technical details enriched by CERT-In and CISA. Given the nature of the flaw, it primarily impacts the confidentiality and integrity of user data within the affected system, with potential secondary impacts on availability if bidding operations are disrupted.

For European organizations using Meon Bidding Solutions, this vulnerability poses a significant risk to the integrity and confidentiality of bidding data. Unauthorized manipulation of bids could lead to financial losses, unfair competitive advantages, and reputational damage. Organizations involved in procurement, auctions, or any competitive bidding processes are particularly vulnerable, as attackers could alter bid submissions or cancel legitimate bids, undermining trust in the bidding process. Additionally, if sensitive user data is accessible through these API endpoints, confidentiality breaches could occur. The impact extends to regulatory compliance, especially under GDPR, where unauthorized access to personal data could result in legal penalties. The medium severity rating reflects that while exploitation requires authentication, the scope of unauthorized access to other user accounts increases the threat level. Disruption of bidding operations could also affect business continuity, especially for companies relying heavily on automated bidding platforms. Given the lack of patches, affected organizations must act swiftly to mitigate risks.

1. Implement strict server-side authorization checks on all API endpoints, ensuring that user-controlled parameters cannot be used to access or manipulate other users' data. 2. Conduct a thorough code review of the API authorization logic, focusing on parameter validation and access control enforcement. 3. Employ parameter whitelisting and enforce strict type and value checks on all inputs related to user identification or authorization keys. 4. Introduce logging and monitoring of API requests to detect anomalous activities such as attempts to access or modify other users' accounts. 5. Restrict API access using role-based access control (RBAC) to limit the scope of actions available to authenticated users. 6. If possible, implement multi-factor authentication (MFA) to reduce the risk of compromised credentials being used to exploit this vulnerability. 7. Engage with Meon to obtain patches or updates addressing this vulnerability and prioritize their deployment once available. 8. As an interim measure, consider isolating or limiting access to the vulnerable API endpoints, or applying web application firewall (WAF) rules to detect and block suspicious parameter manipulations. 9. Educate users and administrators about the risk and encourage prompt reporting of unusual bidding activity.