{"id":"CVE-2026-67194","aliases":["DEBIAN-CVE-2026-67194","EUVD-2026-50414","GHSA-mcmr-g7gg-p242","UBUNTU-CVE-2026-67194"],"status":"published","title":"Courier IMAP \u003c 6.0.1 Mail Server \u003c 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.","severity":{"version":"4.0","score":7.1,"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00548,"percentile":0.46365,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-674"],"published":"2026-07-29T16:39:09Z","modified":"2026-11-08T14:08:07Z","fixes":[{"ecosystem":"Debian:14","package":"courier","fixed_in":["2.0.3-1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.16-3","1.0.16-3.1","1.0.16-3.2","1.3.13-1","1.3.13-10","1.3.13-11","1.3.13-2","1.3.13-3","1.3.13-4","1.3.13-5","1.3.13-6","1.3.13-7","1.3.13-8","1.3.13-9","1.4.1-1","1.4.1-10","1.4.1-2","1.4.1-3","1.4.1-4","1.4.1-5","1.4.1-6","1.4.1-7","1.4.1-8","1.4.1-9","1.5.1-1","1.5.1-2","1.5.1-3","1.5.1-4","2.0.2-1","2.0.2-2","2.0.2-3","2.0.2-4","2.0.3-1","2.0.3-2","2.0.6-1"]},{"source":"osv","ecosystem":"Debian:13","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.1-10","1.4.1-3","1.4.1-3+deb13u1","1.4.1-3+deb13u2","1.4.1-4","1.4.1-5","1.4.1-6","1.4.1-7","1.4.1-8","1.4.1-9","1.5.1-1","1.5.1-2","1.5.1-3","1.5.1-4","2.0.2-1","2.0.2-2","2.0.2-3","2.0.2-4","2.0.3-1","2.0.3-2","2.0.6-1"]},{"source":"osv","ecosystem":"Debian:14","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.3-1"}]}],"versions":["1.4.1-10","1.4.1-3","1.4.1-4","1.4.1-5","1.4.1-6","1.4.1-7","1.4.1-8","1.4.1-9","1.5.1-1","1.5.1-2","1.5.1-3","1.5.1-4","2.0.2-1","2.0.2-2","2.0.2-3","2.0.2-4"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.68.2-1ubuntu5","0.68.2-1ubuntu6","0.68.2-1ubuntu7"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.78.0-2","0.78.0-2ubuntu1","0.78.0-2ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.6-1build1","1.0.6-1build2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.16-3build1","1.0.16-3build2","1.0.16-3build3"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.1-2","1.5.1-4","2.0.6-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"courier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.1-3","1.4.1-10","1.5.1-2"]}],"products":[{"vendor":"svarshavchik","product":"courier imap"},{"vendor":"svarshavchik","product":"courier mail server"}],"references":[{"url":"https://github.com/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F20260627214444","tags":["release-notes","advisory"]},{"url":"https://github.com/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F20260627214309","tags":["release-notes","advisory"]},{"url":"https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e","tags":["patch","fix"]},{"url":"https://packages.debian.org/sid/courier-imap","tags":["product","web"]},{"url":"https://www.vulncheck.com/advisories/courier-imap-mail-server-stack-overflow-dos-via-nested-search-queries","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-67194","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-mcmr-g7gg-p242"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67194.json","tags":["advisory"]},{"url":"https://github.com/svarshavchik/courier","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-67194","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-67194","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-67194","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-67194","title":"Courier IMAP \u003c 6.0.1 Mail Server \u003c 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.","status":"published","published":"2026-07-29T16:39:09.617Z","modified":"2026-11-08T14:08:07.565Z","cvss":[{"version":"4.0","score":7.1,"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","level":"high","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-674"],"updated_at":"2026-11-08T15:43:33.322657Z"}],"euvd":[{"id":"EUVD-2026-50414","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.","status":"published","published":"2026-07-29T16:39:09Z","modified":"2026-11-08T14:08:07Z","cvss":[{"version":"4.0","score":7.1,"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","level":"high"}],"updated_at":"2026-11-08T15:13:07.123106Z"}],"ghsa":[{"id":"GHSA-mcmr-g7gg-p242","title":"Courier IMAP before 6.0.1 and Courier Mail Server before 2.0.2 allow authenticated IMAP users to...","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.","status":"published","published":"2026-07-29T18:31:40Z","modified":"2026-07-29T18:31:46Z","cvss":[{"version":"4.0","score":7.1,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T15:09:54.335538Z"}],"nvd":[{"id":"CVE-2026-67194","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.","status":"published","published":"2026-07-29T17:16:54.017Z","modified":"2026-07-30T20:11:09.18Z","cvss":[{"version":"4.0","score":7.1,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T14:12:33.629616Z"}],"osv":[{"id":"CVE-2026-67194","title":"Courier IMAP \u003c 6.0.1 Mail Server \u003c 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.","status":"published","published":"2026-07-29T16:39:09.617Z","modified":"2026-11-09T07:02:36.131693246Z","cvss":[{"version":"4.0","score":7.1,"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","level":"high"}],"cwes":["CWE-674"],"updated_at":"2026-11-09T03:16:24.800471Z"},{"id":"DEBIAN-CVE-2026-67194","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.","status":"published","published":"2026-07-29T17:16:54.017Z","modified":"2026-10-01T03:03:39.119801486Z","cvss":[{"version":"4.0","score":7.1,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"}],"updated_at":"2026-11-02T15:45:58.699079Z"},{"id":"UBUNTU-CVE-2026-67194","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.","status":"published","published":"2026-07-29T17:16:00Z","modified":"2026-10-17T12:59:19.002049429Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"},{"version":"4.0","score":7.1,"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","level":"high"}],"updated_at":"2026-11-02T16:56:53.710209Z"}]}}