{"id":"CVE-2026-107574","state":"PUBLISHED","title":"Inefficient Algorithmic Complexity in hMailServer","description":"Inefficient algorithmic complexity in the JSON reader of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the mail services unavailable. Reading a JSON object kept the first of each duplicated member name by searching the members already read, so an object of N distinct member names cost O(N^2): 1 MB took 8.9 seconds and 4 MB took 300 seconds against the affected code. A remote attacker reaches the reader without an account by mailing a crafted TLS-RPT report (up to 16 MB after decompression) to a hosted domain's published report mailbox, which is read on a delivery thread; a few such reports hold every delivery thread (ten by default), so the server delivers no mail, local or outbound, for over an hour per report. A signed-in account reaches the same 16 MB body through the webmail's own REST routes, holding the REST API's own worker threads. Where no report mailbox is configured, the unauthenticated REST sign-in routes that read a JSON body are capped at 64 KB and are not affected.","publishedAt":"2026-10-08T11:46:26.206Z","updatedAt":"2026-10-08T14:15:58.279Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"GitLab"},"assigner":"GitLab","products":["Progressive Robot Ltd hMailServer"],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.2.28","status":"affected","lessThan":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":["https://gitlab.com/hmailserver/hmailserver/-/work_items/76","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-2026-107574.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-107574","state":"PUBLISHED","datePublished":"2026-10-08T11:46:26.206Z","dateUpdated":"2026-10-08T14:15:58.279Z","assignerShortName":"GitLab","assignerOrgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","dateReserved":"2026-10-08T10:51:35.642Z"},"containers":{"cna":{"title":"Inefficient Algorithmic Complexity in hMailServer","descriptions":[{"lang":"en","value":"Inefficient algorithmic complexity in the JSON reader of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the mail services unavailable. Reading a JSON object kept the first of each duplicated member name by searching the members already read, so an object of N distinct member names cost O(N^2): 1 MB took 8.9 seconds and 4 MB took 300 seconds against the affected code. A remote attacker reaches the reader without an account by mailing a crafted TLS-RPT report (up to 16 MB after decompression) to a hosted domain's published report mailbox, which is read on a delivery thread; a few such reports hold every delivery thread (ten by default), so the server delivers no mail, local or outbound, for over an hour per report. A signed-in account reaches the same 16 MB body through the webmail's own REST routes, holding the REST API's own worker threads. Where no report mailbox is configured, the unauthenticated REST sign-in routes that read a JSON body are capped at 64 KB and are not affected."}],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.2.28","status":"affected","lessThan":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/76"},{"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:H","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH"}}],"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":"2026-10-08T11:46:26.206Z"},"solutions":[{"lang":"en","value":"Upgrade to hMailServer 6.3.6, which keeps the member names seen in a hash set, so a JSON object is read in one pass. Until then, where domain reports are on, move the report mailbox off a hosted domain; restart the service to end a busy thread."}],"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":"2026-10-08T14:15:32.913666Z","id":"CVE-2026-107574","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":"2026-10-08T14:15:58.279Z"}}]}}}