Vulnerability in Svarshavchik Courier Imap
CVE-2026-67194
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.
EPSS: 0.003 (23.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Svarshavchik Courier Imap — versions 0
- Svarshavchik Courier Mail Server — versions 0
Weakness classification (CWE)
References
- Patch Commit (patch)
- Courier Mail Server Release Notes (release-notes)
- Courier IMAP Release Notes (release-notes)
- Debian Package (product)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-67194?
- CVE-2026-67194 is a medium-severity vulnerability in Svarshavchik Courier Imap, classified under Uncontrolled Recursion. CVSS score: 6.5/10. Published 2026-07-29.
- How severe is CVE-2026-67194?
- Medium severity. CVSS v3 base score is 6.5 out of 10.