Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:H) | High confidentiality impact |
| Integrity (VI:H) | High integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CISA required action
About SmarterTools SmarterMail
CVE-2026-24423 affects SmarterTools SmarterMail, a product from SmarterTools. Before acting, confirm where SmarterTools SmarterMail runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: SmarterTools SmarterMail versions prior to build 9511 contain an unauthenticated remote code execution vulnerability in the ConnectToHub API method. The attacker could point the SmarterMail to the malicious HTTP server, which serves the malicious OS command. This command will be executed by the vulnerable application.
The weakness class is Missing Authentication. A critical function can be used without logging in.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | SmarterTools SmarterMail |
| Affected versions | Smartermail before 100.0.9511 |
| Published | Jan 23, 2026 |
| Last modified | Aug 4, 2026 |
| Added to CISA KEV | Feb 5, 2026 |
| Assigning CNA | disclosure@vulncheck.com |
How to detect it
- Inventory every instance of SmarterTools SmarterMail and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of SmarterTools SmarterMail named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on SmarterTools SmarterMail to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Known exploited, so top priority. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-306: Missing Authentication More CVEs with this weakness
Technical References
Frequently asked questions
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