{"id":"CVE-2026-107572","published":"2026-10-08T12:17:14.870","lastModified":"2026-10-08T21:02:43.860","description":"Inefficient complexity in the Sieve filter evaluation of Progressive Robot hMailServer 6.2.24 through 6.3.5 allows an authenticated account holder to make the mail services unavailable with their own filter. A ':matches' pattern was matched by a backtracking descent whose time grew with the matched value's length raised to the number of wildcards, so a pattern such as '*a*a*a*b' over 800 characters took 44 seconds; and 'deleteheader' erased the fields it removed one at a time, so removing many fields of one name over a message's header cost O(N^2) (80,000 fields took 18.8 seconds). Sieve filters run on the small, shared delivery thread pool, so an account holder whose active script does this, fed a few messages they can send themselves, empties the pool and stops delivery for the whole server. The script is the account holder's own and cannot be set for another user.","cvssScore":6.5,"cvssSeverity":"MEDIUM","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-1333"],"vendors":[],"products":[],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6","tags":[]},{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/75","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}