CVE-2026-107582
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 16% of all known CVEs.
References
Related Vulnerabilities
Other CWE-407 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2020-27223 | Medium | 5.2 | 78% | - | Fix |
| CVE-2022-36021 | Medium | 5.5 | 60% | - | Fix |
| CVE-2021-33582 | High | 7.5 | 3.1% | - | Fix |
| CVE-2024-43485 | High | 7.5 | 3.1% | - | Fix |
| CVE-2024-43484 | High | 7.5 | 3.0% | - | Fix |
| CVE-2016-10396 | High | 7.5 | 2.9% | - | - |
Common questions
How do I fix CVE-2026-107582?
No published fix for CVE-2026-107582 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-107582 being actively exploited?
Not that we know of. CVE-2026-107582 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.26% is the estimated probability that it will be exploited in the next 30 days. That is higher than 16% of all scored CVEs.
How severe is CVE-2026-107582?
CVE-2026-107582 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-08.