{"id":"CVE-2026-67194","state":"PUBLISHED","title":"Courier IMAP < 6.0.1 Mail Server < 2.0.2 Stack Overflow DoS via Nested SEARCH Queries","description":"Courier IMAP before 6.0.1 and Courier Mail Server before 2.0.2 allow authenticated IMAP users to crash the imapd process via deeply nested parenthesized SEARCH queries. The SEARCH command parser (alloc_search_key in searchinfo.C) recursively descends on nested parenthesized groups through a mutual recursion chain with alloc_search_andlist() and alloc_search_notkey(), with no depth limit. Courier IMAP has no overall command line length limit, making exploitation trivial. A single IMAP command with ~2500 nested parentheses overflows the 8MB default stack, causing SIGSEGV.","publishedAt":"2026-07-29T16:39:09.617Z","updatedAt":"2026-08-14T16:50:49.429Z","severity":{"score":7.1,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["svarshavchik Courier IMAP","svarshavchik Courier Mail Server"],"affected":[{"vendor":"svarshavchik","product":"Courier IMAP","packageURL":"pkg:github/svarshavchik/courier","defaultStatus":"affected","versions":[{"version":"0","status":"affected","lessThan":"6.0.1","versionType":"semver"}],"repo":"https://github.com/svarshavchik/courier"},{"vendor":"svarshavchik","product":"Courier Mail Server","packageURL":"pkg:github/svarshavchik/courier","defaultStatus":"affected","versions":[{"version":"0","status":"affected","lessThan":"2.0.2","versionType":"semver"}],"repo":"https://github.com/svarshavchik/courier"}],"references":["https://github.com/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F20260627214444","https://github.com/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F20260627214309","https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e","https://packages.debian.org/sid/courier-imap","https://www.vulncheck.com/advisories/courier-imap-mail-server-stack-overflow-dos-via-nested-search-queries"],"weaknesses":["CWE-674"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/67xxx/CVE-2026-67194.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-67194","state":"PUBLISHED","datePublished":"2026-07-29T16:39:09.617Z","dateUpdated":"2026-08-14T16:50:49.429Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-07-28T16:06:49.774Z"},"containers":{"cna":{"title":"Courier IMAP < 6.0.1 Mail Server < 2.0.2 Stack Overflow DoS via Nested SEARCH Queries","descriptions":[{"lang":"en","value":"Courier IMAP before 6.0.1 and Courier Mail Server before 2.0.2 allow authenticated IMAP users to crash the imapd process via deeply nested parenthesized SEARCH queries. The SEARCH command parser (alloc_search_key in searchinfo.C) recursively descends on nested parenthesized groups through a mutual recursion chain with alloc_search_andlist() and alloc_search_notkey(), with no depth limit. Courier IMAP has no overall command line length limit, making exploitation trivial. A single IMAP command with ~2500 nested parentheses overflows the 8MB default stack, causing SIGSEGV."}],"affected":[{"vendor":"svarshavchik","product":"Courier IMAP","packageURL":"pkg:github/svarshavchik/courier","defaultStatus":"affected","versions":[{"version":"0","status":"affected","lessThan":"6.0.1","versionType":"semver"}],"repo":"https://github.com/svarshavchik/courier"},{"vendor":"svarshavchik","product":"Courier Mail Server","packageURL":"pkg:github/svarshavchik/courier","defaultStatus":"affected","versions":[{"version":"0","status":"affected","lessThan":"2.0.2","versionType":"semver"}],"repo":"https://github.com/svarshavchik/courier"}],"references":[{"url":"https://github.com/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F20260627214444","name":"Courier IMAP Release Notes","tags":["release-notes"]},{"url":"https://github.com/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F20260627214309","name":"Courier Mail Server Release Notes","tags":["release-notes"]},{"url":"https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e","name":"Patch Commit","tags":["patch"]},{"url":"https://packages.debian.org/sid/courier-imap","name":"Debian Package","tags":["product"]},{"url":"https://www.vulncheck.com/advisories/courier-imap-mail-server-stack-overflow-dos-via-nested-search-queries","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"HIGH","baseScore":7.1,"vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}},{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","version":"3.1","baseSeverity":"MEDIUM","baseScore":6.5,"vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-674","lang":"en","description":"Uncontrolled Recursion","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-14T16:50:49.429Z"},"tags":["x_open-source"],"datePublic":"2026-07-29T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:courier-mta:courier_mail_server:*:*:*:*:*:*:*:*","versionEndExcluding":"2.0.2"}]}]}],"credits":[{"lang":"en","value":"Tristan Madani","type":"finder"}],"source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"vulncheck"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-29T18:07:00.293768Z","id":"CVE-2026-67194","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-29T18:07:09.182Z"}}]}}}