CVE-2026-102149 in Email Protection Gateway
Summary
by MITRE • 10/01/2026
Kiteworks Email Protection Gateway did not sufficiently restrict which account a certificate could be assigned to. This could allow an attacker to associate a certificate with another user's account, affecting the confidentiality and integrity of that account's encrypted mail and, where certificate-based login is enabled, potentially permitting unauthorized access to the account.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability in Kiteworks Email Protection Gateway stems from insufficient validation during the process of assigning digital certificates to user accounts. In a properly secured system, the binding between an X.509 certificate and its corresponding identity must be strictly enforced through robust authentication mechanisms that verify ownership of the private key associated with the public key contained within the certificate. However, in this specific instance, the application logic failed to adequately restrict which account could accept or claim a given certificate. This architectural flaw creates a scenario where an attacker who possesses control over a valid digital certificate can manipulate the system's configuration interfaces to associate that certificate with any arbitrary user account within the environment, rather than being limited to the legitimate owner of the private key.
This misconfiguration directly compromises the confidentiality and integrity of encrypted communications associated with the targeted account. Since Kiteworks relies on these certificates for encrypting email traffic, an attacker who successfully binds their own certificate to a victim's account can intercept or decrypt messages intended for that user if they possess the corresponding private key. Furthermore, this flaw undermines the trust model established by public key infrastructure, as it allows malicious actors to impersonate legitimate users in cryptographic operations without possessing the original credentials typically required for such actions.
The operational impact extends beyond data interception when certificate-based login is enabled on the platform. In environments where authentication relies heavily on client certificates rather than traditional username and password combinations, this vulnerability effectively bypasses access controls entirely. An attacker can present their maliciously bound certificate to the gateway, which will then authenticate them as the victim user due to the incorrect association in the backend database or configuration store. This results in unauthorized access to sensitive corporate data stored within the Kiteworks ecosystem, including files and messages that are protected by role-based permissions tied to the compromised account identity.
From a classification perspective, this issue aligns with CWE-284 Improper Access Control, specifically regarding the failure to restrict ownership or binding of security credentials. It also relates closely to CWE-319 Use of Cleartext Protocol for Sensitive Data if the certificate assignment process itself was transmitted without adequate integrity checks during the exploitation phase. In terms of adversary behavior, this technique maps to MITRE ATT&CK Tactic TA0005 Defense Evasion and specifically Technique T1648 Suppression of Security Tools or potentially T1078 Valid Accounts if used for persistent unauthorized access, as it involves manipulating identity attributes to gain foothold.
Mitigation strategies must focus on strengthening the binding process between certificates and user identities. Administrators should ensure that certificate assignment requires multi-factor authentication involving both possession of the private key and verification against existing administrative credentials or directory services like Active Directory. Implementing strict validation checks during the importation of new certificates can prevent orphaned or misassigned keys from being linked to incorrect users. Additionally, enabling audit logging for all certificate management operations allows security teams to detect anomalous associations promptly. Regular reviews of user-certificate mappings and enforcing least privilege principles on who can manage cryptographic identities are essential steps to restore trust in the authentication mechanism and protect against unauthorized access and data exfiltration.