CVE-2026-40013: open-xchange gmbh ox dovecot ce Buffer Underflow
Vulnerability summary
CVE-2026-40013 is a medium (CVSS 4.3) Buffer Underflow vulnerability in open-xchange gmbh ox dovecot ce. EPSS estimates a 0.87% chance of exploitation in the next 30 days, higher than 58% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 3 · Related 2Timeline
- 28-08-2026PublishedVulnerability first disclosed.
- 28-08-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- OSV · DebianEcosystem advisory · calculated4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- NVDNIST4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
EPSS trend
Probability
0.87%
Chance of exploitation in the next 30 days
Percentile
58%
Versus all other CVEs
30-day change
+0.41 pp
From 0.46% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Open-xchange gmbh2 products
- ox dovecot ce≥ 2.3.0, < 2.4.5
- ox dovecot pro≥ 2.3.0, < 2.3.22.2 | ≥ 3.0.0, < 3.0.7 | ≥ 3.1.0, < 3.1.6
Debian1 product
- dovecotAll versions (No fix recorded) | < 1:2.4.1+dfsg1-6+deb13u7 | < 1:2.4.5+dfsg1-1
Ubuntu1 product
- dovecotAll versions (No fix recorded)
3 vendors · 4 products
