CVE-2026-67194Network attack vectorHinoki check available

Authenticated imapd crash via nested SEARCH recursion

Published Jul 29, 2026 · Updated Jul 29, 2026

Uncontrolled recursion in Courier IMAP before 6.0.1 and Courier Mail Server before 2.0.2 allows remote authenticated users to crash imapd. The alloc_search_key function recursively parses parenthesized SEARCH groups through alloc_search_andlist and alloc_search_notkey without a depth limit. Any valid IMAP account can trigger a SIGSEGV with roughly 2,500 nested parentheses, interrupting the imapd service without affecting confidentiality or integrity.

CVSS severity7.1
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Uncontrolled recursion in Courier IMAP before 6.0.1 and Courier Mail Server before 2.0.2 allows remote authenticated users to crash imapd. The alloc_search_key function recursively parses parenthesized SEARCH groups through alloc_search_andlist and alloc_search_notkey without a depth limit. Any valid IMAP account can trigger a SIGSEGV with roughly 2,500 nested parentheses, interrupting the imapd service without affecting confidentiality or integrity.

The record

CVE
CVE-2026-67194
Published
Jul 29, 2026
Updated
Jul 29, 2026
Vendor
Sam Varshavchik
Product
Courier IMAP
Classifications
CWE-674, CAPEC-231, CAPEC-230, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <6.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Sam Varshavchik · Courier IMAPversion=0 <6.0.1
Sam Varshavchik · Courier Mail Serverversion=0 <2.0.2

Published CVSS scores

6.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-674Uncontrolled Recursion
CAPEC-231Oversized Serialized Data Payloads
CAPEC-230Serialized Data with Nested Payloads
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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