Uncontrolled resource consumption in Open-Xchange GmbH OX Dovecot Pro
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Deferred Red Hat: fix deferred
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-400.
Summary
Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Open-Xchange GmbH | OX Dovecot Pro | up to 2.3.0 | — | No fix listed | CNA |
- OX Dovecot Pro VendorOpen-Xchange GmbH Affected up to 2.3.0 Fixed in — No fix listed CNA
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:* | before 2.4.4 | Vulnerable | The Dovecot Project |
| cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:* | before 3.1.5 | Vulnerable | Open-Xchange GmbH |
- cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:* Versions before 2.4.4 Vulnerable ·The Dovecot Project
- cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:* Versions before 3.1.5 Vulnerable ·Open-Xchange GmbH
Remediation
No fixed version listed by the sources yet.
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Advisory ·
Open-Xchange OX Dovecot Pro — documentation.open-xchange.com/dovecot/security/advisories/…
5 records Highest priority Priority MEDIUM 1 MEDIUM, 4 LOW
Other records, highest priority first
- TI-2026-22201 When safe filter is used with variable expansion, all following pipelines on the same…Priority MEDIUM 41
- TI-2026-25985 Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake…Priority LOW 31
- TI-2026-30394 Uncontrolled resource consumption in Open-Xchange GmbH OX Dovecot ProPriority LOW 21
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix planned: Out of support scope |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-40016
- 2026-10-03 Alias added: GHSA-m97m-74mq-mqc6
References
More Open-Xchange GmbH Dovecot vulnerabilities
- TI-2026-22201 When safe filter is used with variable expansion, all following pipelines on the same… CVSS 3.1CRITICAL 9.1
- TI-2026-22208 Uncontrolled resource consumption in Open-Xchange GmbH OX Dovecot Pro CVSS 3.1HIGH 7.5
- TI-2025-36674 Improper input validation in Open-Xchange GmbH OX Dovecot Pro CVSS 3.1HIGH 7.5
- TI-2025-36670 Improper input validation in Open-Xchange GmbH OX Dovecot Pro CVSS 3.1HIGH 7.5
- TI-2026-19360 SQL injection in Open-Xchange GmbH OX Dovecot Pro CVSS 3.1HIGH 8.2
- TI-2026-22206 Improper authentication in Open-Xchange GmbH OX Dovecot Pro CVSS 3.1HIGH 7.4
Sources
- CVE-2026-40016 · CVE Program
- CVE-2026-40016 · NVD
- FIRST EPSS
- GHSA-m97m-74mq-mqc6 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-40016 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences