CVE-2026-107582Inefficient Algorithmic Complexity in hMailServer
Updated under an hour ago ()
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It affects Progressive Robot Ltd hMailServer. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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Inefficient algorithmic complexity in the REST API (6.3.3 through 6.3.5) and the IMAP PREVIEW response (6.2.22 through 6.3.5) of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the webmail, the administration console and the REST API unavailable by sending a message. To show a snippet of each message in a folder's message list, the server decoded the character entity references of a message that has an HTML part and no text part with a string replacement whose work grew with the square of their number. A received HTML-only message holding a very large number of entity references therefore keeps one of the listener's four worker threads busy for minutes or longer each time the recipient's webmail lists the folder, without the message being opened, so that a few such listings leave the HTTP listener unable to answer anybody. The IMAP PREVIEW response read such text the same way, holding an IMAP thread for each client that asks for the preview of such a message. The flaw is in the server's shared string class, whose replace and remove both ran in quadratic time.
- CVSS
- 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-407
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitLab
- NVD analysis
- Deferred
- Record last updated
- Oct 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Progressive Robot Ltd hMailServer progressive_robot:hmailserver (from the name) | from 6.2.22-pre1 before 6.3.6 | CNA record |
References
- https://gitlab.com/hmailserver/hmailserver/-/work_items/67
- https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.