CVE-2026-100741 Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in hMailServer
Remote attackers can execute arbitrary JScript in hMailServer via crafted passwords if event scripting is enabled, leading to service account compromise.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-100741?
CVE-2026-100741 is a critical code injection vulnerability in Progressive Robot Ltd hMailServer, published on 27 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Eval injection in the JScript event-script dispatcher in Progressive Robot Ltd's hMailServer, versions 6.0.0 through 6.3.3 on Windows, allows a remote, unauthenticated attacker to run arbitrary JScript inside the hMailServer service process, with the privileges of the service account, via a password containing a backslash followed by an apostrophe, sent in any logon (SMTP AUTH, POP3, IMAP) that names an existing, active account. Exploitation requires a non-default configuration: event scripting enabled (off by default), the script language set to JScript (the default is VBScript), and an OnClientValidatePassword handler defined in the event script. The server wrote event values into the handler call as JScript string literals, escaping the apostrophe but not the backslash, so such a value closes the literal and the rest of it is parsed as script. The same flaw is reachable by a remote POP3 server through the message UID it returns, where an OnExternalAccountDownload handler is defined, and by a remote SMTP server through the error reply it rejects a delivery with, where an OnDeliveryFailed handler is defined. Before 6.2.25 the injected script can create any COM object, and from 6.2.25 it can with the default ScriptAllowedObjects value of '*'; WScript.Shell among them gives command execution as the service account. VBScript event scripts and the Linux builds of Progressive Robot Ltd's hMailServer are not affected.
Weakness: CWE-95
Which versions are affected by CVE-2026-100741?
How do I fix CVE-2026-100741?
No fix has been published for CVE-2026-100741 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-100741 being exploited?
There is no known exploitation of CVE-2026-100741 in the wild and no public exploit code.
Sources
Also known as GHSA-v6j4-p35g-mq6p.