CVE-2026-40203
Last modified
CVE-2026-40203 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. EPSS estimates a 0.22% chance of exploitation in the next 30 days.
Description
When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.
Metrics
Weakness Enumeration
Affected Software
Source: CNA advisory (CVE.org). NVD analysis pending.
| Vendor | Product | Versions |
|---|---|---|
| Open-Xchange GmbH | OX Dovecot Pro | >= 2.3.0, < 2.3.22.2; >= 3.0.0, < 3.0.7; >= 3.1.0, < 3.1.6 |
| Open-Xchange GmbH | OX Dovecot CE | >= 2.3.0, < 2.4.5 |
References
Timeline
- Published
- Last Modified
- Status
- Deferred
Frequently Asked Questions
What is CVE-2026-40203?
How severe is CVE-2026-40203?
How do I fix CVE-2026-40203?
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-40197Incus is a system container and virtual machine manager. In …6.5
- CVE-2026-40198Net::CIDR::Lite versions before 0.23 for Perl does not valid…7.5
- CVE-2026-40199Net::CIDR::Lite versions before 0.23 for Perl mishandles IPv…6.5
- CVE-2026-4020The Gravity SMTP plugin for WordPress is vulnerable to Sensi…7.5
- CVE-2026-40200An issue was discovered in musl libc 0.7.10 through 1.2.6. S…8.1
- CVE-2026-40201@diplodoc/search-extension 1.0.0 through 3.x before 3.0.3 al…5.4
- CVE-2026-40204None None None No publicly available exploits are known.3.1
- CVE-2026-40205An attacker that holds an OAuth2 token granting only part of…5.9
- CVE-2026-40208An attacker might be able to delay the processing of DoH3 qu…3.7
- CVE-2026-40209An attacker might be able to cause outgoing TCP connections …5.3
- CVE-2026-4021The Contest Gallery plugin for WordPress is vulnerable to an…8.1
- CVE-2026-40210An out-of-bounds read might happen when SetMacAddrAction is …4.8
Are you affected by CVE-2026-40203?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST