CVE-2026-67194

svarshavchik Courier IMAPVulnerabilityCVSS 7.1

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.

No public exploitation has been reported so far. No distribution fix is listed yet; apply vendor mitigations and monitor.

Recommended action: Track your distribution's security tracker and apply the fix as soon as it ships.

CVE-2026-67194 svarshavchik Courier IMAP Vulnerability

Severity metrics

CVSS 4.0 : 7.1 HIGH · CVSS 3.1 : 6.5 MEDIUM

Attack vectorNetwork (remote)

Attack complexityLow

Attack requirementsNone

Privileges requiredLow

User interactionNone

Confidentiality impactNone

Integrity impactNone

Availability impactHigh

Subsequent confidentialityNone

Subsequent integrityNone

Subsequent availabilityNone

Vector: AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Affected & fixed versions by distribution

Versions are the native distribution strings (backport-aware): RHEL/Debian/SUSE backport fixes, so compare with the distro version comparator (dpkg / rpm / vercmp), not the upstream version.

No affected package in the tracked watchlist yet (Debian, Ubuntu, Arch, SUSE, Red Hat...). Triage may still be pending.

Sources

Advisory NVD CVE.org

Published 2026-07-29 · source: NVD