CVE-2026-104083
MediumCVSS 6.1Summary
SmarterMail before build 9777 contains a stored mutation cross-site scripting vulnerability that allows remote attackers to inject executable script by placing payloads inside a <style> element nested within MathML foreign content (<math><mtext><mglyph>), which the custom HTML sanitizer treats as inert CDATA text but browsers reparse as live markup. Attackers can deliver a crafted calendar (iCal) message containing an <img src=x onerror=...> payload that executes automatically in the recipient's webmail session at /interface/message-iframe when the message is opened, enabling script execution and data exfiltration unconstrained by the interface's permissive Content-Security-Policy.
Risk Assessment
An attacker can execute arbitrary JavaScript in the victim's webmail session, leading to data theft and account takeover. This may compromise the confidentiality and integrity of communications.
Recommendation
Update SmarterMail to build 9777 or later. In the meantime, consider tightening the Content-Security-Policy and monitoring for suspicious messages.
Other vulnerabilities in SmarterMail
See all- CVE-2026-104084High
SmarterMail before build 9777 contains a privilege escalation vulnerability where JWT access and refresh tokens embed a role claim at issuance that is not revalidated against the account's current role when redeemed through POST /api/v1/auth/refresh-token. Attackers who capture a refresh token issued before an administrator demotion, or a demoted user whose session was not actively polling at the time of demotion, can replay the stale token to obtain a new access token retaining the higher-privilege role.
- CVE-2026-104082High
SmarterMail before build 9777 contains a remote code execution vulnerability that allows an attacker holding a SysAdmin-scoped access token to bypass the Volume Mount script-directory containment control by provisioning a new mail domain with an arbitrary FileStore root path inside the trusted Scripts directory via the domain-put endpoint. Attackers can disclose the Scripts path through the AddOrUpdateMount endpoint, clear the upload extension blacklist via the global-mail endpoint, then upload a malicious script through the ordinary mail file-storage upload API so that saving a CommandMount triggers RunScript before validation, resulting in a reverse shell executing as the SmarterMail service account with SYSTEM-level privileges.
- CVE-2026-23760CriticalActively exploited
SmarterTools SmarterMail versions prior to build 9511 contain an authentication bypass vulnerability in the password reset API. The force-reset-password endpoint permits anonymous requests and fails to verify the existing password or a reset token when resetting system administrator accounts. An unauthenticated attacker can supply a target administrator username and a new password to reset the account, resulting in full administrative compromise of the SmarterMail instance. NOTE: SmarterMail system administrator privileges grant the ability to execute operating system commands via built-in management functionality, effectively providing administrative (SYSTEM or root) access on the underlying host.
Original NVD description (English source)
SmarterMail before build 9777 contains a stored mutation cross-site scripting vulnerability that allows remote attackers to inject executable script by placing payloads inside a <style> element nested within MathML foreign content (<math><mtext><mglyph>), which the custom HTML sanitizer treats as inert CDATA text but browsers reparse as live markup. Attackers can deliver a crafted calendar (iCal) message containing an <img src=x onerror=...> payload that executes automatically in the recipient's webmail session at /interface/message-iframe when the message is opened, enabling script execution and data exfiltration unconstrained by the interface's permissive Content-Security-Policy.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS