CVE-2025-41441 Overview
CVE-2025-41441 affects Synck Mailform Pro CGI versions prior to 4.3.4. The application generates verbose error messages that expose sensitive information to unauthenticated remote users. A remote attacker can trigger these error conditions over the network to obtain coupon codes issued by the application. The flaw is classified under [CWE-209: Generation of Error Message Containing Sensitive Information]. Only deployments that enable the coupon feature are affected.
Critical Impact
Unauthenticated remote attackers can harvest coupon codes by triggering application error messages, enabling fraud against merchants using the coupon feature.
Affected Products
- Synck Mailform Pro CGI versions prior to 4.3.4
- Deployments where the coupon feature is enabled
- Web forms built on the affected Mailform Pro CGI runtime
Discovery Timeline
- 2025-05-26 - CVE-2025-41441 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-41441
Vulnerability Analysis
Mailform Pro CGI is a Japanese web form processor widely used on e-commerce and contact pages. The vulnerability resides in the coupon handling logic, where the application returns verbose diagnostic output when input validation fails. Instead of returning a generic failure response, the error handler embeds internal state, including valid coupon code values, into the response body served to the client.
An unauthenticated attacker submits a crafted form request that intentionally triggers coupon validation errors. The server responds with an error page that discloses coupon codes stored or referenced by the application. Because the endpoint is reachable over the network without credentials, the attacker can automate probing at scale.
The impact is limited to confidentiality of coupon data. Integrity and availability of the underlying application are not directly affected. However, disclosed coupon codes can be redeemed by attackers, resulting in financial loss for the merchant.
Root Cause
The root cause is improper error handling under [CWE-209]. The developer included variable content in error responses without sanitizing what should remain server-side. Coupon codes intended for authorized customers become part of the debug output returned to any HTTP client.
Attack Vector
The attack vector is network based and requires no authentication or user interaction. An attacker sends HTTP requests to the vulnerable form endpoint with parameters that force the coupon module into an error state. The response payload contains the sensitive coupon values. See the JVN Security Advisory JVN39546799 and the SyncK Blog Post for vendor details.
Detection Methods for CVE-2025-41441
Indicators of Compromise
- Repeated HTTP requests to Mailform Pro CGI form endpoints containing malformed or unexpected coupon parameters
- HTTP responses containing error strings alongside coupon code values in the response body
- Spikes in coupon redemptions from IP addresses that never completed a normal purchase flow
- Access log entries from single sources iterating through form submissions at high rates
Detection Strategies
- Inspect web server access logs for high volumes of POST requests to mailformpro endpoints returning non-200 responses
- Deploy web application firewall rules that flag response bodies containing coupon patterns paired with error keywords
- Correlate coupon redemption events with the source IP history to identify codes redeemed by users who never legitimately received them
Monitoring Recommendations
- Enable full response logging on the reverse proxy fronting Mailform Pro CGI to retain forensic evidence
- Alert on any 4xx or 5xx response from the coupon submission handler that exceeds a defined baseline
- Track outbound coupon issuance versus redemption ratios to surface abnormal fraud patterns
How to Mitigate CVE-2025-41441
Immediate Actions Required
- Upgrade Mailform Pro CGI to version 4.3.4 or later immediately
- Disable the coupon feature until the upgrade is applied if patching is not possible
- Rotate any coupon codes that may have been exposed while the vulnerable version was in production
- Review web server access logs for prior exploitation attempts against form endpoints
Patch Information
Synck released Mailform Pro CGI version 4.3.4 to remediate this issue. The fix removes sensitive coupon information from error responses. Administrators should download the updated release from the vendor and follow the migration steps in the SyncK Blog Post.
Workarounds
- Turn off the coupon feature in the Mailform Pro CGI configuration until the patch is applied
- Place a reverse proxy or WAF in front of the application to strip or replace error response bodies containing coupon-like tokens
- Restrict access to the form endpoint by IP allow-listing where the form is used only by known partners
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
