CVE-2026-67194 json
Courier IMAP < 6.0.1 Mail Server < 2.0.2 Stack Overflow DoS via Nested SEARCH Queries
published 2026-07-29 3 mo ago modified 2026-11-08 26 h ago also EUVD-2026-50414
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 46%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- svarshavchik Courier IMAP 6.0.1
- svarshavchik Courier Mail Server 2.0.2
- courier Debian 14 2.0.3-1
debian advisories DEBIAN-CVE-2026-67194
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 3 mo ago
Exploit prediction
0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 7.1 | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| CNA | 4.0 | 7.1 | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected products
- svarshavchik Courier IMAP
- svarshavchik Courier Mail Server
Classification
- Weakness
-
- CWE-674 Uncontrolled Recursion
References
-
github.com
/svarshavchik/courier-libs/commit/b5b5581aabea3efadf5e2944947ff0214aa3533e
patch
-
github.com
/svarshavchik/courier/releases/tag/courier-imap%2F6.0.1%2F20260627214444
release-notes
-
github.com
/svarshavchik/courier/releases/tag/courier%2F2.0.2%2F20260627214309
release-notes
-
packages.debian.org
/sid/courier-imap
product
-
vulncheck.com
/advisories/courier-imap-mail-server-stack-overflow-dos-via-nested-search-queries
third-party-advisory
Sources
- CVE List CVE-2026-67194
- NVD CVE-2026-67194
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.