High severity · published Oct 9, 2026
CVE-2026-104084
SmarterMail < Build 9777 Stale JWT Role Claim Privilege Escalation via Refresh Token
8.8
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 24% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SM
Smartermail · Smartertools
before Build 9777 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-104084
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-104084
release-notes
https://www.smartertools.com/smartermail/release-notes/current#/9526:~:text=Build%209777%20(Oct%208%2C%202026)
technical-description
https://blog.evan.lat/posts/sm/
third-party-advisory
https://www.vulncheck.com/advisories/smartermail-build-9777-stale-jwt-role-claim-privilege-escalation-via-refresh-token
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