# CVE-2021-40110: Apache James IMAP vulnerable to a ReDoS

> An attacker can cause a Denial of Service in Apache James by sending crafted IMAP LIST commands that trigger expensive regular expression backtracking.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Jan 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-r58x-wjg8-63m9

## What is CVE-2021-40110?

CVE-2021-40110 is a high-severity denial of service vulnerability in Apache James, published on 4 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2021-40110?

2 open source packages ship an affected version, including org.apache.james:james-server. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.james:james-server` | Maven | From 3.1.0 | 3.6.1 |
| `org.apache.james:james-server` | Maven | From 3.1.0 | 3.6.1 |

Products: Apache James.

## How do I fix CVE-2021-40110?

Upgrade org.apache.james:james-server to 3.6.1 or later.

## Is CVE-2021-40110 being exploited?

There is no known exploitation of CVE-2021-40110 in the wild and no public exploit code.

## Other vulnerabilities in Apache James

- [CVE-2023-51518](https://insights.sbomify.com/CVE-2023-51518/): Apache James server: Privilege escalation via JMX pre-authentication deserialisation (critical 9.8)
- [CVE-2019-0228](https://insights.sbomify.com/CVE-2019-0228/): Vulnerability that affects org.apache.pdfbox:pdfbox (critical 9.8)
- [CVE-2021-40525](https://insights.sbomify.com/CVE-2021-40525/): Sieve file storage vulnerable to path traversal attacks (critical 9.1)
- [CVE-2023-26269](https://insights.sbomify.com/CVE-2023-26269/): Apache James server: Privilege escalation through unauthenticated JMX (high 7.8)
- [CVE-2006-2806](https://insights.sbomify.com/CVE-2006-2806/): Denial of service in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40110 and fix it if it is affected.

What it is: CVE-2021-40110 is a high-severity denial of service vulnerability in Apache James, published on 4 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-40110 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.james:james-server (Maven): affected from 3.1.0; fixed in 3.6.1
- org.apache.james:james-server (Maven): affected from 3.1.0; fixed in 3.6.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-40110/ (Markdown: https://insights.sbomify.com/CVE-2021-40110/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40110
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40110
- OSV: https://osv.dev/vulnerability/CVE-2021-40110

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40110/
Summaries are generated and may contain mistakes; the official description above is the record.