CVE-2026-107577

7.5 HIGH

Published 2026-10-08 · Updated 2026-10-08

AI risk analysis

Summary: A flaw in Progressive Robot hMailServer allows remote attackers to cause indefinite loops during MIME message processing, leading to complete service unavailability. The vulnerability occurs when processing malformed MIME headers with empty parameters followed by semicolons, causing worker threads to hang indefinitely.
Exploitability: Exploitation is straightforward requiring only a single specially crafted email message with malformed MIME headers; no authentication is needed and the attack can be launched from anywhere on the internet.
Blast radius: The impact could be severe as the service becomes completely unresponsive until restart, affecting all IMAP, SMTP, and POP3 connections, REST API endpoints, and message delivery functions simultaneously.
Detection: No reliable host or network indicator is derivable from the published description.
Prioritized remediation: Upgrade to hMailServer 6.3.6 or later to receive the fix for the infinite loop in MIME header processing.

maildosmime

Analysis generated locally by garnet-coder (no data left the box). AI-assisted — verify against primary sources before acting.

NVD description

Inefficient algorithmic complexity and a non-terminating loop in the MIME processing of received messages in Progressive Robot hMailServer 6.0.0 through 6.3.5 allow a remote unauthenticated attacker to make the mail services unavailable by sending a message. Removing a MIME header parameter whose value is empty and directly followed by a semicolon (for example a Content-Disposition with 'filename=a.bat; filename=;') entered a loop that never terminates, holding a worker thread at full load until the server is restarted; this is reached when the attachment blocker renames a blocked attachment or a filename is set over the REST API. Separately, decoding a header field that holds many RFC 2047 encoded words of an encoding other than base64 or quoted-printable, removing a parameter with many RFC 2231 continuations, and deleting many header fields of one name each took time growing with the square of the message, on the small thread pools that serve IMAP, SMTP and POP3 connections, delivery and the REST API.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weaknesses

CWE-835

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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