CVE-2026-102105 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 renders message content that references external resources. Depending on the services reachable from the gateway, this could disclose sensitive internal information or trigger unintended actions on internal systems.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified in Kiteworks Email Protection Gateway prior to version 9.5.0 represents a critical Server-Side Request Forgery (SSRF) flaw that undermines the integrity of the email processing pipeline. This weakness stems from insufficient validation and sanitization of external resource references embedded within message content processed by the gateway. When an attacker crafts an email containing links or image sources pointing to internal network addresses, the server-side component responsible for rendering this content blindly executes HTTP requests on behalf of the user without verifying whether the destination is authorized or intended. This architectural oversight allows a remote, unauthenticated actor to manipulate the application into making requests that were not anticipated by the system designers, effectively turning the gateway into a proxy for internal network reconnaissance and exploitation.
From a technical perspective, this flaw aligns with CWE-918, which defines Server-Side Request Forgery as a weakness where a web server retrieves a specified resource from a user-supplied URL without validating that request. In the context of Kiteworks Email Protection Gateway, the rendering engine processes external resources such as images or stylesheets to display email content correctly in various clients. By injecting malicious URLs pointing to internal services like database interfaces, administrative panels, or cloud metadata endpoints, an attacker can force the gateway to interact with these systems. The vulnerability is particularly dangerous because it operates at the application layer and does not require authentication, allowing any sender of a crafted email to exploit this condition. This behavior maps directly to MITRE ATT&CK technique T1598.002, specifically Phishing for Information via Inbound Email, where the attacker uses social engineering combined with technical exploitation to gain initial access or gather intelligence from within the network perimeter.
The operational impact of this vulnerability is severe and multifaceted. First, it enables unauthorized disclosure of sensitive internal information by allowing attackers to probe internal services that are typically shielded from external access. For instance, if the gateway can reach internal database servers or API endpoints, an attacker could extract configuration details, user credentials, or proprietary data stored within those systems. Second, the vulnerability facilitates unintended actions on internal infrastructure. If critical management interfaces or IoT devices are accessible from the network segment where the email gateway resides, attackers could trigger commands, modify configurations, or even achieve remote code execution depending on the specific services exposed. This effectively bypasses traditional perimeter defenses such as firewalls and intrusion detection systems that rely on source IP reputation rather than application-layer logic validation.
To mitigate this risk, organizations running Kiteworks Email Protection Gateway versions earlier than 9.5.0 must apply the vendor-provided patch immediately to address the input validation deficiencies in the content rendering engine. In addition to upgrading, security teams should implement network-level controls such as strict egress filtering rules that restrict outbound connections from the email gateway server to only known and necessary external domains. Utilizing a proxy with allow-listing capabilities can further enforce this restriction by intercepting and validating all outgoing requests before they leave the DMZ or internal segment. Furthermore, deploying web application firewalls configured to detect SSRF patterns in HTTP request headers and bodies provides an additional layer of defense against exploitation attempts while patching efforts are underway. Regular auditing of outbound traffic logs from email infrastructure components is also recommended to identify any anomalous connection attempts that may indicate active probing by attackers exploiting this weakness.