Progressive Robot hMailServer up to 6.3.5 Webmail certificate validation

Summaryinfo

A vulnerability described as problematic has been identified in Progressive Robot hMailServer up to 6.3.5. This impacts an unknown function of the component Webmail. Executing a manipulation can lead to certificate validation. This vulnerability is handled as CVE-2026-107587. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Progressive Robot hMailServer up to 6.3.5 and classified as problematic. This vulnerability affects an unknown code block of the component Webmail. The manipulation with an unknown input leads to a certificate validation vulnerability. The CWE definition for the vulnerability is CWE-295. The product does not validate, or incorrectly validates, a certificate. As an impact it is known to affect integrity. CVE summarizes:

Improper certificate validation in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote unauthenticated attacker to have S/MIME-encrypted mail that the account later sends to another correspondent also encrypted to the attacker's key. When its recipient opened a signed message, the webmail kept the signer's certificate for encrypting replies whether or not the server found its chain trusted, under the first e-mail address the certificate listed rather than the message's From address, and beside any certificate already held for that address. Encrypted mail later sent from the webmail to that address was encrypted to every certificate held for it, so a holder of the kept certificate's key who obtains a copy of such a message can read it.

The advisory is shared for download at gitlab.com. This vulnerability was named CVE-2026-107587 since 10/08/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1587.003.

Upgrading to version 6.3.6 eliminates this vulnerability.

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Productinfo

Type

• Mail Server Software

Vendor

• Progressive Robot

Name

• hMailServer

Version

• 6.3.0
• 6.3.1
• 6.3.2
• 6.3.3
• 6.3.4
• 6.3.5

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CPE 2.2info

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