What’s Vulnerable › Vulnerabilities

CVE-2026-104084: SmarterMail < Build 9777 Stale JWT Role Claim Privilege Escalation via Refresh Token

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-09 · updated 2026-10-27
• Weakness: CWE-613

Description

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 (such as DomainAdmin or SysAdmin) until natural token expiry.

Affected products

• SmarterTools SmarterMail: before Build 9777 — fixed in Build 9777

How to fix

Upgrade to a fixed version: SmarterTools SmarterMail Build 9777. Check the vendor advisory for mitigations.

References

• https://blog.evan.lat/posts/sm/
• https://www.smartertools.com/smartermail/release-notes/current#/9526:~:text=Build%209777%20(Oct%208%2C%202026)
• https://www.vulncheck.com/advisories/smartermail-build-9777-stale-jwt-role-claim-privilege-escalation-via-refresh-token

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