{"id":"CVE-2026-107575","published":"2026-10-08T12:17:15.333","lastModified":"2026-10-08T21:02:43.860","description":"Inefficient algorithmic complexity in the SPF macro expansion of Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to consume worker-thread time by publishing a crafted SPF record. RFC 7208 section 7.1 requires a name too long to look up to lose whole labels from the left; the server did this by removing one label at a time and copying the rest of the name each time, so the work grew with the square of the expansion. An attacker who publishes an SPF record for a domain they control, with a mechanism whose domain-spec expands through macros to a name far longer than 253 characters, makes the SPF check of a message from that domain take several seconds. The expansion is bounded by SPF's own per-term and per-macro limits, so the loss of availability is partial.","cvssScore":5.3,"cvssSeverity":"MEDIUM","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwes":["CWE-407"],"vendors":[],"products":[],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6","tags":[]},{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/74","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}