Vulnerability 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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947f
- https://github.com/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F202606272
- https://github.com/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F2026
- https://packages.debian.org/sid/courier-imap
- https://www.vulncheck.com/advisories/courier-imap-mail-server-stack-overflow-dos
FAQ
What is CVE-2026-67194?
CVE-2026-67194 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 (allo...
How severe is CVE-2026-67194?
CVE-2026-67194 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-67194?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.