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MEDIUM severity

CVE-2021-40111 — james-server

MEDIUM

CVE-2021-40111 is a medium-severity (CVSS 6.5) CWE-835 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.

Infinite Loop in Apache James

Also known asGHSA-fqgw-6qj5-8hmp
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs81th percentile — riskier than 81% of all scored CVEsHighest risk
0.23%1.03%1.83%2.62%0.7%2.1%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-40111 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, while fuzzing with Jazzer the IMAP parsing stack, we discover that crafted APPEND and STATUS IMAP command could be used to trigger infinite loops resulting in expensive CPU computations and OutOfMemory exceptions. This can be used for a Denial Of Service attack. The IMAP user needs to be authenticated to exploit this vulnerability. This affected Apache James prior to version 3.6.1. This vulnerability had been patched in Apache James 3.6.1 and higher. We recommend the upgrade.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.james:james-serverall versions3.6.1org.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-2021-40111 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, while fuzzing with Jazzer the IMAP parsing stack, we discover that crafted APPEND and STATUS IMAP command could be used to trigger infinite loops resulting in expensive CPU computations and OutOfMemory exceptions. This can be used for a Denial Of Service attack. The IMAP user needs to be authenticated to exploit this vulnerability. This affected Apache James prior to version 3.6.1. This vulnerability had been patched in Apache James 3.6.1 and higher. We recommend the upgrade.
O3 Security · Impact-Aware SCA

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CVE-2021-40111: james-server DoS — Fixed in 3.6.1