DoS via Memory Exhaustion in managesieve (Dovecot)
CVE-2026-27858 Published on March 27, 2026
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 Analysis
CVE-2026-27858 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-27858 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-27858
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Affected Versions
Open-Xchange GmbH OX Dovecot Pro:- Before and including 2.3.0 is affected.
- Before and including 3.1.0 is affected.
- Before and including 2.4.0 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.