Vulnerability · Published Aug 28, 2026 · Assigned by OX
CVE-2026-40013
Medium 4.3
In plain English
A medium-severity security flaw in OX Dovecot CE from Open-Xchange GmbH. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 59% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
An attacker that has valid credentials can submit a Sieve script containing an extreme numeric literal, which causes an out-of-bounds write when the ManageSieve service compiles the script. This causes memory corruption and an observed crash of the ManageSieve process, resulting in denial of service for script management. This might be able to be used for remote code execution. Disable the ManageSieve service if users do not need remote Sieve script management. Update to non-vulnerable version. No publicly available exploits are known.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | dovecot | 1:2.3.19.1+dfsg1-2.1+deb12u7 | DEBIAN-CVE-2026-40013 |
| Debian:13 | dovecot | 1:2.4.1+dfsg1-6+deb13u7 | DEBIAN-CVE-2026-40013 |
| Debian:14 | dovecot | 1:2.4.5+dfsg1-1 | DEBIAN-CVE-2026-40013 |
| Ubuntu:22.04:LTS | dovecot | no fix listed | UBUNTU-CVE-2026-40013 |
| Ubuntu:24.04:LTS | dovecot | no fix listed | UBUNTU-CVE-2026-40013 |
| Ubuntu:26.04:LTS | dovecot | no fix listed | UBUNTU-CVE-2026-40013 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Open-Xchange GmbH | OX Dovecot Pro | 2.3.0 – before 2.3.22.23.0.0 – before 3.0.73.1.0 – before 3.1.6 |
| Open-Xchange GmbH | OX Dovecot CE | 2.3.0 – before 2.4.5 |
Weakness: CWE-124 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L