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.
{
"cna_assigner": "VulnCheck",
"cwe_ids": [
"CWE-674"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/67xxx/CVE-2026-67194.json",
"unresolved_ranges": [
{
"extracted_events": [
{
"fixed": "6.0.1"
},
{
"fixed": "2.0.2"
}
],
"source": "AFFECTED_FIELD"
},
{
"extracted_events": [
{
"fixed": "2.0.2"
}
],
"source": "CPE_FIELD"
},
{
"extracted_events": [
{
"fixed": "6.0.1"
},
{
"fixed": "2.0.2"
}
],
"source": "DESCRIPTION"
}
]
}"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-67194.json"
[
{
"deprecated": false,
"digest": {
"line_hashes": [
"324102191788101242559591669349694290702",
"35235881022085087855072741834168207339",
"22998871602831633174075279873829851744"
],
"threshold": 0.9
},
"id": "CVE-2026-67194-50345343",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e",
"target": {
"file": "imap/searchinfo.h"
}
}
]
"2026-08-15T09:53:25Z"