CVE-2016-10073 in Forums
Summary
by MITRE
The from method in library/core/class.email.php in Vanilla Forums before 2.3.1 allows remote attackers to spoof the email domain in sent messages and potentially obtain sensitive information via a crafted HTTP Host header, as demonstrated by a password reset request.
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Analysis
by VulDB Data Team • 01/27/2025
The vulnerability identified as CVE-2016-10073 resides within the Vanilla Forums platform, specifically in the email handling mechanism located in library/core/class.email.php. This flaw represents a critical security weakness that enables remote attackers to manipulate the email domain identification within sent messages, potentially leading to sophisticated social engineering attacks and information disclosure. The vulnerability affects versions prior to 2.3.1, indicating a significant window of exposure for affected installations.
The technical implementation of this vulnerability stems from improper validation of the HTTP Host header within the email sending functionality. When the from method processes email transmission, it fails to properly sanitize or validate the host information provided in the HTTP request headers. This allows attackers to craft malicious Host headers that contain spoofed domain information, which then gets embedded into the email headers of sent messages. The flaw essentially permits the modification of the email sender domain without proper authentication or validation checks.
The operational impact of this vulnerability extends beyond simple email spoofing, as it can be leveraged to create highly convincing phishing attempts and credential theft operations. Attackers can craft password reset requests that appear to originate from legitimate domains within the target organization, making it significantly more difficult for users to identify malicious communications. This vulnerability directly relates to CWE-20 Improper Input Validation and CWE-611 Improper Restriction of XML External Entity Reference, as it involves inadequate validation of external input and potential information disclosure through crafted headers. The attack vector aligns with ATT&CK technique T1566.001 Spearphishing Attachment, where the spoofed email domain can be used to increase the success rate of social engineering campaigns.
The security implications of this vulnerability are particularly severe in environments where email authentication mechanisms such as SPF, DKIM, and DMARC are not properly implemented or enforced. An attacker could exploit this vulnerability to bypass these protections by creating messages that appear legitimate from the target domain, potentially leading to successful credential compromise or data exfiltration. The flaw also enables potential information gathering attacks where attackers can probe system configurations or gather sensitive data through crafted email headers that are processed by the vulnerable forum software. Organizations using affected versions of Vanilla Forums should immediately implement security patches or mitigate the vulnerability through web application firewalls and header validation mechanisms to prevent exploitation.
This vulnerability demonstrates the critical importance of proper input validation in web applications, particularly within email handling components that process user-supplied data. The flaw highlights the need for comprehensive security testing of all input sources, including HTTP headers, and reinforces the principle that email systems should not trust information provided in headers without proper validation. The vulnerability serves as a reminder that seemingly minor implementation flaws in core functionality can have significant security implications, particularly when they involve user-facing communication systems that are frequently targeted by attackers.