Resource exhaustion in Dovecot
CVE-2026-27858
Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.010 (63.7th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 63.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.010 · change: +0.002
Affected products
Weakness classification (CWE)
References
- documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2… (vendor-advisory, Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-27858?
- CVE-2026-27858 is a high-severity vulnerability in Dovecot, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-03-27.
- How severe is CVE-2026-27858?
- High severity. CVSS v3 base score is 7.5 out of 10.