CVE-2017-14077 in Securimage
Summary
by MITRE
HTML Injection in Securimage 3.6.4 and earlier allows remote attackers to inject arbitrary HTML into an e-mail message body via the $_SERVER['HTTP_USER_AGENT'] parameter to example_form.ajax.php or example_form.php.
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Analysis
by VulDB Data Team • 12/08/2019
The vulnerability identified as CVE-2017-14077 represents a critical HTML injection flaw within the Securimage CAPTCHA implementation version 3.6.4 and earlier. This security weakness resides in the way the system processes user input, specifically targeting the $_SERVER['HTTP_USER_AGENT'] parameter that is commonly used to track browser information. The vulnerability manifests when the application fails to properly sanitize or escape user-supplied data before incorporating it into email message bodies, creating a pathway for malicious actors to inject arbitrary HTML content.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP headers, particularly the User-Agent string that browsers automatically send to web servers. When an attacker crafts a malicious User-Agent header and submits it through the vulnerable form handling scripts example_form.ajax.php or example_form.php, the application processes this input without adequate validation or sanitization. The insecure code pattern allows the injected HTML to be embedded directly into the email message body that is generated and sent by the system, effectively bypassing normal security controls designed to prevent cross-site scripting attacks.
This vulnerability operates under the Common Weakness Enumeration framework as CWE-79, which specifically addresses Cross-Site Scripting (XSS) vulnerabilities. The operational impact of this flaw extends beyond simple HTML injection, as it can enable attackers to perform various malicious activities including phishing attempts, credential harvesting, or redirection to malicious websites. The remote nature of the attack means that exploitation can occur from anywhere on the internet without requiring local system access or prior authentication. The vulnerability affects the integrity of email communications and can compromise the trust relationship between users and the application, as recipients may receive messages containing malicious code that could execute in their email clients or web browsers.
The implications of this vulnerability align with tactics described in the MITRE ATT&CK framework under the category of Initial Access, specifically leveraging web application vulnerabilities to gain unauthorized access. Attackers can leverage this flaw to establish persistent access points or to deliver payloads that exploit other vulnerabilities in the email ecosystem. The impact is particularly severe for organizations that rely on email-based communication and verification processes, as the injected HTML could contain links to malicious domains or embedded scripts designed to capture user credentials or install malware. Organizations using vulnerable versions of Securimage should immediately implement mitigations including input validation, output encoding, and parameter sanitization to prevent exploitation.
Mitigation strategies should focus on implementing proper input validation mechanisms that filter or escape all user-supplied data before processing. The recommended approach includes applying strict sanitization to HTTP headers, implementing Content Security Policy headers to limit script execution, and upgrading to patched versions of Securimage that address this vulnerability. Organizations should also consider implementing web application firewalls to detect and block suspicious User-Agent strings and establish monitoring procedures to identify potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input validation in web applications and demonstrates how seemingly innocuous parameters can become attack vectors when not properly secured.