CVE-2020-28200Network attack vector

Mail delivery denial of service via regex exhaustion

Published Jun 28, 2021 · Updated Aug 4, 2024

Uncontrolled resource consumption in Dovecot before 2.3.15 allows remote authenticated users to interrupt mail delivery via Sieve scripts. The Sieve interpreter executes CPU-intensive regular expressions without limiting per-script or cumulative CPU time. A user able to install an abusive Sieve script can exhaust CPU or reach LMTP/LDA process limits, causing partial or complete denial of service.

CVSS severity4.3
Medium
EPSS probability1.97%
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 Dovecot before 2.3.15 allows remote authenticated users to interrupt mail delivery via Sieve scripts. The Sieve interpreter executes CPU-intensive regular expressions without limiting per-script or cumulative CPU time. A user able to install an abusive Sieve script can exhaust CPU or reach LMTP/LDA process limits, causing partial or complete denial of service.

The record

CVE
CVE-2020-28200
Published
Jun 28, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3OX Software GmbHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P

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-770Allocation of Resources Without Limits or Throttling
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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