CVE-2026-107581 (CVSS 6.5)

Description

Progressive Robot hMailServer 6.0.0 through 6.3.5 processes several IMAP commands from a signed-in account in time quadratic in the command's length or in the number of elements it names, and can be made to hold memory out of proportion to a command. The FETCH data-item parser normalised a BODY[] section with a case-insensitive string replacement that copied the whole item per occurrence and split the item list by repeatedly copying the remainder of the command; the server's case-insensitive search compared a needle afresh at every position, so a long SEARCH TEXT key over a message cost the product of the two lengths; SEARCH message sets and the saved-result marker ($), SORT criteria, HEADER.FIELDS name lists and UID ranges were each read once per message rather than once per command; and a FETCH naming a message's sections very many times read and held every section in memory before sending any. An IMAP command may continue past one line through non-synchronizing literals, so one command can reach about eleven megabytes. The IMAP worker threads are a small pool shared with SMTP and POP3, so a signed-in user sending such commands can make the IMAP, SMTP and POP3 services stop responding (CWE-407) and can consume excessive memory (CWE-400).

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CVSS v3.1 Score

6.5

MEDIUM

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

Weakness Type (CWE)

CWE-407 CWE-407

References

Other References

https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6 https://gitlab.com/hmailserver/hmailserver/-/work_items/68

Frequently Asked Questions

What is CVE-2026-107581? +

Progressive Robot hMailServer 6.0.0 through 6.3.5 processes several IMAP commands from a signed-in account in time quadratic in the command's length or in the number of elements it names, and can be made to hold memory out of proportion to a command. The FETCH data-item parser normalised a BODY[] section with a case-insensitive string replacement that copied the whole item per occurrence and split the item list by repeatedly copying the remainder of the command; the server's case-insensitive search compared a needle afresh at every position, so a long SEARCH TEXT key over a message cost the product of the two lengths; SEARCH message sets and the saved-result marker ($), SORT criteria, HEADER.FIELDS name lists and UID ranges were each read once per message rather than once per command; and a FETCH naming a message's sections very many times read and held every section in memory before sending any. An IMAP command may continue past one line through non-synchronizing literals, so one command can reach about eleven megabytes. The IMAP worker threads are a small pool shared with SMTP and POP3, so a signed-in user sending such commands can make the IMAP, SMTP and POP3 services stop responding (CWE-407) and can consume excessive memory (CWE-400). It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-107581? +

CVE-2026-107581 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2026-107581? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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