CVE-2021-40111Network attack vector

Authenticated denial of service via IMAP parser loops

Published Jan 4, 2022 · Updated Aug 4, 2024

Denial of service in Apache James Server before 3.6.1 allows remote authenticated users to interrupt mail service via crafted IMAP commands. The APPEND and STATUS command parsers enter infinite loops on crafted command syntax, consuming CPU and potentially exhausting JVM memory. A valid IMAP account is required, and successful exploitation hangs or crashes the service without reported data disclosure or modification.

CVSS severity6.5
Medium
EPSS probability2.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Apache James Server before 3.6.1 allows remote authenticated users to interrupt mail service via crafted IMAP commands. The APPEND and STATUS command parsers enter infinite loops on crafted command syntax, consuming CPU and potentially exhausting JVM memory. A valid IMAP account is required, and successful exploitation hangs or crashes the service without reported data disclosure or modification.

The record

CVE
CVE-2021-40111
Published
Jan 4, 2022
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache James Server
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 4, 2022CVE 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?

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

  1. Affected versionversion=Apache James <=3.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Apache Software Foundation · Apache James Serverversion=Apache James <=3.6.0

Published CVSS scores

6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/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-835Loop with Unreachable Exit Condition ('Infinite Loop')
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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