CVE-2026-102102 in Email Protection Gateway
Summary
by MITRE • 10/01/2026
Kiteworks Email Protection Gateway before version 9.5.0 is vulnerable to Server-Side Request Forgery (SSRF). A server-side request forgery (SSRF) weakness in Kiteworks Email Protection Gateway could allow a remote, unauthenticated attacker to induce the gateway to issue crafted requests to internal or otherwise unintended network destinations. The requests are triggered while the gateway retrieves an issuer certificate in an inbound message. Depending on the services reachable from the gateway, this could disclose sensitive internal information or disrupt gateway operation.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified in Kiteworks Email Protection Gateway versions prior to 9.5.0 represents a critical Server-Side Request Forgery (SSRF) flaw that compromises the integrity of email security infrastructure by allowing unauthenticated actors to manipulate server-side network interactions. This weakness specifically manifests during the certificate validation process for inbound messages, where the gateway attempts to retrieve an issuer certificate from a URL embedded within the message metadata or headers. Because the application fails to adequately validate or sanitize these URLs before processing them, it permits external entities to dictate which internal resources are accessed by the backend system. The absence of authentication requirements exacerbates this risk, as any remote attacker with network access can exploit this mechanism without needing valid credentials, effectively turning a routine security check into an attack vector for lateral movement and data exfiltration within the protected environment.
From a technical perspective, the core issue lies in the insufficient validation of user-supplied input used to construct outbound HTTP or HTTPS requests initiated by the gateway itself. When processing inbound emails, the system extracts certificate authority information and attempts to fetch corresponding certificates from specified endpoints. If an attacker crafts an email containing a maliciously constructed URL pointing to internal services such as cloud metadata endpoints, local administrative interfaces, or other sensitive backend systems, the gateway will blindly follow this directive. This behavior aligns with CWE-918, which classifies Server-Side Request Forgery as a weakness where a web server retrieves content from a user-supplied URL without proper validation of the destination's legitimacy and safety. The attacker can leverage common internal IP ranges or localhost addresses to probe for open ports, sensitive configuration files, or authentication tokens that are not exposed to the public internet but remain accessible via the gateway’s network interface.
The operational impact of this vulnerability is severe, potentially leading to significant data breaches and service disruptions depending on the architecture of the protected network. By inducing the gateway to make requests to internal destinations, an attacker can disclose sensitive information such as database credentials, API keys, or proprietary business logic stored in internal services. Furthermore, if specific internal services are vulnerable to other attacks when accessed from the gateway’s IP address, this SSRF can serve as a pivot point for further exploitation within the network perimeter. In worst-case scenarios, an attacker could target critical infrastructure components like load balancers, monitoring systems, or even attempt to disrupt gateway operations by causing denial-of-service conditions through resource exhaustion on internal targets. This undermines the primary function of the Email Protection Gateway, which is to secure communications and filter threats, thereby exposing the organization to both confidentiality and availability risks.
To mitigate this vulnerability, organizations running Kiteworks Email Protection Gateway versions earlier than 9.5.0 must prioritize immediate patching to upgrade to version 9.5.0 or later, where these input validation controls have been strengthened. Until patches are applied, defensive measures should include implementing strict network segmentation to limit the gateway’s ability to reach sensitive internal subnets and configuring firewall rules to block outbound connections from the gateway to non-essential internal IP ranges. Additionally, deploying web application firewalls with SSRF detection capabilities can help identify and block malicious request patterns attempting to access metadata services or local interfaces. Security teams should also monitor logs for unusual outbound connection attempts originating from the email gateway, particularly those targeting private IP addresses or known cloud metadata endpoints like 169.254.169.254, which are commonly targeted in SSRF attacks as documented in MITRE ATT&CK technique T1557, Adversary-in-the-Middle, where attackers intercept communications to steal credentials and other sensitive information.