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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
svarshavchik Courier IMAP
Default version status: affected
0 to < 6.0.1affected
pkg:github/svarshavchik/couriersvarshavchik Courier Mail Server
Default version status: affected
0 to < 2.0.2affected
pkg:github/svarshavchik/courierReferences
- https://github.com/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F20260627214444 ↗
- https://github.com/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F20260627214309 ↗
- https://github.com/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e ↗
- https://packages.debian.org/sid/courier-imap ↗
- https://www.vulncheck.com/advisories/courier-imap-mail-server-stack-overflow-dos-via-nested-search-queries ↗