CVE-2026-67194
Published:July 29, 2026
Updated:August 04, 2026
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 Packages
https://github.com/svarshavchik/courier-libs.git (GITHUB):
Affected version(s) >=courier/2.0.0/20260620164119 <courier/2.0.2/20260627214309Fix Suggestion:
Update to version courier/2.0.2/20260627214309https://github.com/svarshavchik/courier-libs.git (GITHUB):
Affected version(s) >=courier-imap/5.3.2/20260111153337 <courier-imap/6.0.1/20260627214444Fix Suggestion:
Update to version courier-imap/6.0.1/20260627214444Related Resources (8)
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Contact UsCVSS v4
Base Score:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Uncontrolled Recursion
EPSS
Base Score:
0.30