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HIGH severity

CVE-2021-40110 — james-server

HIGH

CVE-2021-40110 is a high-severity (CVSS 7.5) vulnerability in org.apache.james:james-server. A fix is available for org.apache.james:james-server — see the affected versions and patch details below.

Denial of Service in Apache James

Also known asGHSA-r58x-wjg8-63m9
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs86th percentile — riskier than 86% of all scored CVEsHighest risk
0.02%1.18%2.35%3.52%0.7%2.9%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-40110 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
☕org.apache.james:james-server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.james:james-server≥ 3.1.0&&< 3.6.13.6.1org.apache.james:james-server:3.6.1

Affected Products

1 product · 1 configurations
Application
jamesapache
< 3.6.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.james:james-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.james:james-server to 3.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-40110 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2021-40110: james-server DoS — Fixed in 3.6.1