{"api_version":"1","generated_at":"2026-10-08T14:53:10+00:00","cve":"CVE-2026-107582","urls":{"html":"https://cve.report/CVE-2026-107582","api":"https://cve.report/api/cve/CVE-2026-107582.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-107582","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-107582"},"summary":{"title":"Inefficient Algorithmic Complexity in hMailServer","description":"Inefficient algorithmic complexity in the REST API (6.3.3 through 6.3.5) and the IMAP PREVIEW response (6.2.22 through 6.3.5) of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the webmail, the administration console and the REST API unavailable by sending a message. To show a snippet of each message in a folder's message list, the server decoded the character entity references of a message that has an HTML part and no text part with a string replacement whose work grew with the square of their number. A received HTML-only message holding a very large number of entity references therefore keeps one of the listener's four worker threads busy for minutes or longer each time the recipient's webmail lists the folder, without the message being opened, so that a few such listings leave the HTTP listener unable to answer anybody. The IMAP PREVIEW response read such text the same way, holding an IMAP thread for each client that asks for the preview of such a message. The flaw is in the server's shared string class, whose replace and remove both ran in quadratic time.","state":"PUBLISHED","assigner":"GitLab","published_at":"2026-10-08 12:17:16","updated_at":"2026-10-08 12:17:16"},"problem_types":["CWE-407","CWE-407 CWE-407: Inefficient Algorithmic Complexity"],"metrics":[{"version":"3.1","source":"cve@gitlab.com","type":"Secondary","score":"6.5","severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","baseScore":6.5,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"6.5","severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":6.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","version":"3.1"}}],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6","name":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6","refsource":"cve@gitlab.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/67","name":"https://gitlab.com/hmailserver/hmailserver/-/work_items/67","refsource":"cve@gitlab.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-107582","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107582","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Progressive Robot Ltd","product":"hMailServer","version":"affected 6.2.22-pre1 6.3.6 semver","platforms":[]}],"timeline":[],"solutions":[{"source":"CNA","title":"","value":"Upgrade to hMailServer 6.3.6, whose string replacement and removal write their result in one pass. Until then: lower the maximum message size, which bounds the cost (it grows with the square of the HTML's size); remove such a message over IMAP or POP3; or keep the REST listener off (RestApiPort 0, the default).","time":"","lang":"en"}],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Found in the hMailServer project's own security review (Progressive Robot Ltd)","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"hMailServer","repo":"https://gitlab.com/hmailserver/hmailserver","vendor":"Progressive Robot Ltd","versions":[{"lessThan":"6.3.6","status":"affected","version":"6.2.22-pre1","versionType":"semver"}]}],"credits":[{"lang":"en","type":"finder","value":"Found in the hMailServer project's own security review (Progressive Robot Ltd)"}],"descriptions":[{"lang":"en","value":"Inefficient algorithmic complexity in the REST API (6.3.3 through 6.3.5) and the IMAP PREVIEW response (6.2.22 through 6.3.5) of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the webmail, the administration console and the REST API unavailable by sending a message. To show a snippet of each message in a folder's message list, the server decoded the character entity references of a message that has an HTML part and no text part with a string replacement whose work grew with the square of their number. A received HTML-only message holding a very large number of entity references therefore keeps one of the listener's four worker threads busy for minutes or longer each time the recipient's webmail lists the folder, without the message being opened, so that a few such listings leave the HTTP listener unable to answer anybody. The IMAP PREVIEW response read such text the same way, holding an IMAP thread for each client that asks for the preview of such a message. 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Until then: lower the maximum message size, which bounds the cost (it grows with the square of the HTML's size); remove such a message over IMAP or POP3; or keep the REST listener off (RestApiPort 0, the default)."}],"title":"Inefficient Algorithmic Complexity in hMailServer"}},"cveMetadata":{"assignerOrgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","assignerShortName":"GitLab","cveId":"CVE-2026-107582","datePublished":"2026-10-08T11:48:26.083Z","dateReserved":"2026-10-08T10:52:15.637Z","dateUpdated":"2026-10-08T11:48:26.083Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-08 12:17:16","lastModifiedDate":"2026-10-08 12:17:16","problem_types":["CWE-407","CWE-407 CWE-407: Inefficient Algorithmic Complexity"],"metrics":{"cvssMetricV31":[{"source":"cve@gitlab.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","baseScore":6.5,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":3.6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"107582","Ordinal":"1","Title":"Inefficient Algorithmic Complexity in hMailServer","CVE":"CVE-2026-107582","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"107582","Ordinal":"1","NoteData":"Inefficient algorithmic complexity in the REST API (6.3.3 through 6.3.5) and the IMAP PREVIEW response (6.2.22 through 6.3.5) of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the webmail, the administration console and the REST API unavailable by sending a message. To show a snippet of each message in a folder's message list, the server decoded the character entity references of a message that has an HTML part and no text part with a string replacement whose work grew with the square of their number. A received HTML-only message holding a very large number of entity references therefore keeps one of the listener's four worker threads busy for minutes or longer each time the recipient's webmail lists the folder, without the message being opened, so that a few such listings leave the HTTP listener unable to answer anybody. The IMAP PREVIEW response read such text the same way, holding an IMAP thread for each client that asks for the preview of such a message. The flaw is in the server's shared string class, whose replace and remove both ran in quadratic time.","Type":"Description","Title":"Inefficient Algorithmic Complexity in hMailServer"}]}}}