CVE-2025-11441 is a vulnerability identified in the JhumanJ OpnForm product, specifically affecting versions 1.9.0 through 1.9.3. The vulnerability arises from improper restriction of excessive authentication attempts due to inadequate handling of the X-Forwarded-For HTTP header within the HTTP Header Handler component. Attackers can manipulate this header to circumvent rate limiting or lockout mechanisms designed to prevent brute-force attacks on authentication endpoints. This flaw allows remote attackers to perform repeated authentication attempts without triggering protective restrictions, increasing the risk of credential stuffing or password guessing attacks. The attack complexity is high, indicating that exploitation requires detailed knowledge of the system and crafted requests, but no privileges or user interaction are required. The vulnerability has a CVSS 4.0 base score of 6.3, reflecting medium severity, with network attack vector, high attack complexity, and no privileges or user interaction needed. Although a public exploit exists, there are no confirmed reports of active exploitation in the wild. The vendor has released a patch (commit 11e99960e14ca986b1a001a56e7533223d2cfa5b) that addresses the issue by properly restricting authentication attempts and validating the X-Forwarded-For header. Organizations using affected versions of OpnForm should prioritize patching to mitigate the risk. Additional security controls such as enhanced monitoring of authentication attempts, anomaly detection, and network-level rate limiting can further reduce exposure.

For European organizations, this vulnerability poses a risk of unauthorized access through brute-force or credential stuffing attacks, potentially compromising sensitive data and systems. Since OpnForm is used for form handling, exploitation could lead to unauthorized submission or retrieval of data, impacting confidentiality and integrity. The improper restriction of authentication attempts could also facilitate account takeover attacks, leading to further lateral movement within networks. The medium severity indicates moderate impact, but the high complexity and lack of widespread exploitation reduce immediate risk. However, organizations in sectors with high regulatory requirements (e.g., finance, healthcare, government) could face compliance issues and reputational damage if exploited. The vulnerability could also be leveraged as a stepping stone for more advanced attacks if combined with other weaknesses. Therefore, European entities using OpnForm should consider this a significant risk, especially if they handle personal data protected under GDPR or other regulations.

1. Apply the official patch identified by commit 11e99960e14ca986b1a001a56e7533223d2cfa5b immediately to all affected OpnForm instances. 2. Implement additional rate limiting and lockout mechanisms at the web application firewall (WAF) or reverse proxy level to detect and block excessive authentication attempts regardless of header manipulation. 3. Monitor authentication logs for unusual patterns, such as repeated attempts from varying IP addresses or suspicious X-Forwarded-For header values. 4. Enforce multi-factor authentication (MFA) on all accounts to reduce the risk of account compromise even if credentials are guessed. 5. Conduct regular security assessments and penetration tests focusing on authentication mechanisms and header validation. 6. Educate security teams about this vulnerability and ensure incident response plans include detection and mitigation steps for brute-force attacks exploiting this flaw. 7. Where possible, restrict or validate the use of X-Forwarded-For headers at the network perimeter to prevent spoofing. 8. Keep all related infrastructure components (e.g., proxies, load balancers) updated to support proper header handling and security controls.