Overview
CVE-2025-55129 describes a username handling vulnerability in Revive Adserver that allows for impersonation attacks. Discovered by HackerOne community members, this vulnerability persists despite previous attempts to fix similar issues (CVE-2025-52672). The core issue stems from the ability to create user accounts with usernames that visually resemble existing accounts, primarily through the use of homoglyphs (characters that look similar to others).
Technical Details
Following the attempted fix for CVE-2025-52672, Kassem S.(kassem_s94) discovered alternate techniques to exploit the username handling within Revive Adserver. The vulnerability lies in the insufficient sanitization or validation of usernames during account creation and login. Attackers can register new accounts using usernames that contain homoglyphs – characters from different alphabets that appear identical or very similar to standard ASCII characters (e.g., using Cyrillic “а” instead of Latin “a”). This can deceive users and administrators, allowing attackers to potentially gain unauthorized access or perform malicious actions under the guise of a legitimate user. The independent reports from itz_hari_ and khoof further highlight the pervasive nature of homoglyph-based impersonation within the system.
CVSS Analysis
The CVSS score is currently not available (N/A) for CVE-2025-55129. This is likely because the full impact and exploitability details are still being assessed. However, given the potential for impersonation and unauthorized access, the vulnerability is likely to be rated as at least a Medium severity. A more precise CVSS score will depend on factors such as the ease of exploitation, the scope of impact (e.g., limited to specific actions or affecting all users), and the privileges required to carry out the attack.
Possible Impact
The potential impact of CVE-2025-55129 is significant. Successful exploitation can lead to:
- Account Takeover: Impersonation can be used to trick legitimate users into revealing credentials.
- Unauthorized Access: Attackers can gain access to sensitive data or administrative functionalities.
- Reputation Damage: Malicious actions performed under the guise of a legitimate user can damage the reputation of the organization using Revive Adserver.
- Data Manipulation: Attackers might be able to modify or delete critical data within the ad server.
- Financial Loss: Fraudulent activities using the impersonated account.
Mitigation and Patch Steps
Until a patch is released, the following mitigation steps are recommended:
- Implement Strict Username Validation: Enforce stringent username validation rules to prevent the use of homoglyphs and other visually similar characters. Consider whitelisting allowed character sets.
- Multi-Factor Authentication (MFA): Implement MFA to add an extra layer of security, even if an attacker manages to impersonate a user.
- User Awareness Training: Educate users on how to identify and avoid phishing attacks and impersonation attempts.
- Monitor User Activity: Regularly monitor user activity for suspicious behavior, such as logins from unusual locations or unexpected changes to account settings.
- Contact Revive Adserver Support: Reach out to Revive Adserver support and request an official patch to address this vulnerability.
