CVE-2026-27857Network attack vector

Service interruption via persistent NOOP memory allocations

Published Mar 27, 2026 · Updated Mar 27, 2026

Uncontrolled resource consumption in Open-Xchange Dovecot Pro 2.3.0 and earlier allows remote authenticated users to interrupt service. The imap-login NOOP parser retains about 1 MB while processing 4,000 paired parentheses and permits the allocation to persist when no terminating LF arrives. Roughly 1,000 concurrent IMAP connections can exhaust the process VSZ limit, kill the process, and terminate other proxied connections.

CVSS severity4.3
Medium
EPSS probability0.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Open-Xchange Dovecot Pro 2.3.0 and earlier allows remote authenticated users to interrupt service. The imap-login NOOP parser retains about 1 MB while processing 4,000 paired parentheses and permits the allocation to persist when no terminating LF arrives. Roughly 1,000 concurrent IMAP connections can exhaust the process VSZ limit, kill the process, and terminate other proxied connections.

The record

CVE
CVE-2026-27857
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
Open-Xchange GmbH
Product
Dovecot Pro
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=2.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open-Xchange GmbH · Dovecot Proversion=0 <=2.3.0

Published CVSS scores

4.3Open-XchangeCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5redhat-SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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