CVE-2026-93483 Vulnerability Analysis & Exploit Details

CVE-2026-93483 Vulnerability Summary

CVE-2026-93483: In Znuny through 7.3.6, an attacker can bypass specific standard login procedures and gain unauthorized access to sensitive system functions by manipulating a specific HTTP request header. Because the application incorrectly trusts this header, an attacker can impersonate any user, including administrators, without requiring a password. This grants full access to confidential data and system controls. More specifically, the HTTPBasicAuth modules for the agent (Kernel::System::Auth::HTTPBasicAuth) and customer (Kernel::System::CustomerAuth::HTTPBasicAuth) interfaces read the username to log in not only from $ENV{REMOTE_USER} (set by the web server after successful authentication), but also, as a fallback, from $ENV{HTTP_REMOTE_USER}, which is populated directly from an attacker-controllable "Remote-User" request header. On systems where HTTPBasicAuth was configured as the authentication backend, this allowed an attacker to log in as any existing user by sending a request with a forged Remote-User header, without providing any credentials.

CVE-2026-93483 References

External References

• https://www.znuny.org/advisories
• https://www.znuny.org/en/advisories/zsa-2026-14

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Cache Poisoning CAPEC-141 An attacker exploits the functionality of cache technologies to cause specific data to be cached that aids the attackers' objectives. This describes any attack whereby an attacker places incorrect or harmful material in cache. The targeted cache can be an application's cache (e.g. a web browser cache) or a public cache (e.g. a DNS or ARP cache). Until the cache is refreshed, most applications or clients will treat the corrupted cache value as valid. This can lead to a wide range of exploits including redirecting web browsers towards sites that install malware and repeatedly incorrect calculations based on the incorrect value.
• DNS Cache Poisoning CAPEC-142 A domain name server translates a domain name (such as www.example.com) into an IP address that Internet hosts use to contact Internet resources. An adversary modifies a public DNS cache to cause certain names to resolve to incorrect addresses that the adversary specifies. The result is that client applications that rely upon the targeted cache for domain name resolution will be directed not to the actual address of the specified domain name but to some other address. Adversaries can use this to herd clients to sites that install malware on the victim's computer or to masquerade as part of a Pharming attack.
• User-Controlled Filename CAPEC-73 An attack of this type involves an adversary inserting malicious characters (such as a XSS redirection) into a filename, directly or indirectly that is then used by the target software to generate HTML text or other potentially executable content. Many websites rely on user-generated content and dynamically build resources like files, filenames, and URL links directly from user supplied data. In this attack pattern, the attacker uploads code that can execute in the client browser and/or redirect the client browser to a site that the attacker owns. All XSS attack payload variants can be used to pass and exploit these vulnerabilities.
• Manipulating Web Input to File System Calls CAPEC-76 An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
• AJAX Footprinting CAPEC-85 This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.

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