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JamesApplication · Apache

CVE-2021-40110

HIGH · 7.5 CVSS v3.1 Published 2022-01-04
Fix available
A fix is available. Upgrade to 3.6.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In Apache James, using Jazzer fuzzer, we identified that an IMAP user can craft IMAP LIST commands to orchestrate a Denial Of Service using a vulnerable Regular expression. This affected Apache James prior to 3.6.1 We recommend upgrading to Apache James 3.6.1 or higher , which enforce the use of RE2J regular expression engine to execute regex in linear time without back-tracking.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Apache James IMAP server prior to 3.6.1 contains a vulnerable Regular expression in the IMAP LIST command handler that allows an authenticated IMAP user to craft malicious commands causing catastrophic backtracking (ReDoS), leading to Denial of Service. The fix in version 3.6.1+ replaces the regex engine with RE2J which executes in linear time without backtracking.

MitigationUpgrade Apache James to version 3.6.1 or higher which enforces the RE2J regular expression engine to prevent ReDoS attacks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JamesApplication
Affected:< 3.6.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Apache James installation
    Check if Apache James server is installed on the system by searching for James-related processes, directories, or configuration files (commonly in /opt/james, /usr/share/james, or similar paths). Look for the 'james' process or the 'conf' directory containing James configuration.
    Affected if Apache James server is present on the system
  2. Determine Apache James version
    Locate and read the version file or check the JAR manifest. Common locations include the run script, a VERSION file in the installation directory, or the james-server-*.jar manifest. Run: find / -name 'james*' -o -name 'VERSION*' 2>/dev/null to locate version information.
    Affected if The installed version is below 3.6.1 (e.g., 3.6.0, 3.5.0, etc.)
  3. Verify IMAP service is enabled
    Check the James configuration file (typically conf/james-database.properties or conf/imapserver.xml) to confirm the IMAP protocol is enabled and listening. Look for <imapserver> enabled='true' or similar configuration.
    Affected if IMAP protocol is enabled in the James configuration (required for the attack vector)
  4. Confirm network exposure of IMAP port
    Check if port 143 (IMAP) or 993 (IMAPS) is open and listening. Use commands like netstat -tulpn | grep -E '143|993' or ss -tulpn | grep -E '143|993' to verify the IMAP service is network-accessible.
    Affected if The IMAP port is exposed on a reachable network interface, allowing remote authenticated attackers to send malicious commands

The environment is affected if Apache James server version 3.6.0 or earlier is installed with IMAP protocol enabled and network-accessible, enabling an authenticated user to trigger ReDoS via specially crafted IMAP LIST commands.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.6.1 or later
Fixed in 3.6.1
Interim mitigation

Upgrade Apache James to version 3.6.1 or higher which enforces the RE2J regular expression engine to prevent ReDoS attacks.

Recommended fix High confidence

Apache James 3.6.1 or higher

  1. Backup your current Apache James configuration and data
  2. Download Apache James 3.6.1 or higher from the official Apache James distribution
  3. Review the upgrade documentation for migration steps
  4. Install Apache James 3.6.1 or higher
  5. Verify that the RE2J regular expression engine is being used
  6. Test IMAP LIST functionality to confirm the DoS vulnerability is resolved
Caveat Switching to RE2J regex engine may break existing custom regex patterns that relied on Java regex backtracking features

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in James Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-40110 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data