Quick answers
- Is CVE-2026-126616 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-126616 being exploited in the wild.
- How severe is CVE-2026-126616?
- Medium severity, with a CVSS score of 5.3, published 11 November 2026.
- Which products and versions are affected?
- Progressive Robot hMailServer 6.2.0 through 6.3.3.
- Is there a fix for CVE-2026-126616?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-126616 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-126616?
- Check whether you run Progressive Robot hMailServer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability stems from a mismatch between MySQL tables created in utf8 character set (which cannot store characters outside the Basic Multilingual Plane) and SASL PLAIN usernames decoded as UTF-8 (which can contain such characters). When a username with an out-of-plane character is used in the failed logon that would trigger a ban, the database rejects the INSERT of the auto-ban rule due to character encoding constraints. The count of failed attempts is cleared but the address is not added to the ban list, resetting the attack counter and allowing the attacker unbounded login attempts. The vulnerability requires MySQL or MariaDB backend and affects multiple authentication protocols (POP3, IMAP, SMTP AUTH PLAIN where enabled).
Affected products
- Progressive Robot hMailServer 6.2.0 through 6.3.3
Timeline
- 2026-11-11: disclosed