{"id":"CVE-2026-107575","state":"PUBLISHED","title":"Inefficient Algorithmic Complexity in hMailServer","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.","publishedAt":"2026-10-08T11:46:46.082Z","updatedAt":"2026-10-08T14:17:04.989Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitLab"},"assigner":"GitLab","products":["Progressive Robot Ltd hMailServer"],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.3.4","status":"affected","lessThan":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":["https://gitlab.com/hmailserver/hmailserver/-/work_items/74","https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"],"weaknesses":["CWE-407"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/107xxx/CVE-2026-107575.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-107575","state":"PUBLISHED","datePublished":"2026-10-08T11:46:46.082Z","dateUpdated":"2026-10-08T14:17:04.989Z","assignerShortName":"GitLab","assignerOrgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","dateReserved":"2026-10-08T10:51:40.639Z"},"containers":{"cna":{"title":"Inefficient Algorithmic Complexity in hMailServer","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.3.4","status":"affected","lessThan":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/74"},{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-407","lang":"en","description":"CWE-407: Inefficient Algorithmic Complexity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitLab","orgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","dateUpdated":"2026-10-08T11:46:46.082Z"},"solutions":[{"lang":"en","value":"Upgrade to hMailServer 6.3.6, which finds where the name becomes short enough and cuts it once. Until then, turn SPF checking off, or accept the bounded delay."}],"credits":[{"lang":"en","value":"Found in the hMailServer project's own security review (Progressive Robot Ltd)","type":"finder"}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-08T14:16:55.314371Z","id":"CVE-2026-107575","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-08T14:17:04.989Z"}}]}}}