# CVE-2021-30640: Auth weakness in JNDIRealm

> Attackers can bypass authentication or lockout protections in Apache Tomcat by manipulating JNDI Realm username variations.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jul 2021
- **Updated:** 8 Oct 2026
- **Also known as:** BIT-tomcat-2021-30640, DEBIAN-CVE-2021-30640, GHSA-36qh-35cm-5w2w, OESA-2021-1299, UBUNTU-CVE-2021-30640

## What is CVE-2021-30640?

CVE-2021-30640 is a medium-severity authentication bypass vulnerability in Apache Tomcat, published on 12 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the JNDI Realm of Apache Tomcat allows an attacker to authenticate using variations of a valid user name and/or to bypass some of the protection provided by the LockOut Realm. This issue affects Apache Tomcat 10.0.0-M1 to 10.0.5; 9.0.0.M1 to 9.0.45; 8.5.0 to 8.5.65.

Weakness: CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2021-30640?

7 open source packages ship an affected version, including org.apache.tomcat:tomcat and tomcat. It affects 7 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.tomcat:tomcat` | Maven | From 10.0.0-M1 | 10.0.5 |
| `org.apache.tomcat:tomcat` | Maven | From 10.0.0-M1 | 10.0.5 |
| `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.65 |
| `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.65 |
| `org.apache.tomcat:tomcat` | Maven | From 9.0.0M1 | 9.0.45 |
| `org.apache.tomcat:tomcat` | Maven | From 9.0.0M1 | 9.0.45 |
| `tomcat` | Bitnami | From 7.0.0 | 7.0.109, 8.5.66, 9.0.46, 10.0.6 |

Products: Apache Tomcat, Debian Debian Linux, Oracle Communications Cloud Native Core Policy, Oracle Communications Diameter Signaling Router, Oracle Communications Pricing Design Center, Oracle Hospitality Cruise Shipboard Property Management System, Oracle Tekelec Platform Distribution.

## How do I fix CVE-2021-30640?

Upgrade org.apache.tomcat:tomcat to a fixed version for your release line: 10.0.5, 8.5.65 or 9.0.45.

## Is CVE-2021-30640 being exploited?

There is no known exploitation of CVE-2021-30640 in the wild and no public exploit code.

## Other vulnerabilities in Apache Tomcat

- [CVE-2025-24813](https://insights.sbomify.com/CVE-2025-24813/): Apache Tomcat Path Equivalence (critical 10.0, exploited in the wild)
- [CVE-2016-8735](https://insights.sbomify.com/CVE-2016-8735/): Apache Tomcat Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2017-12617](https://insights.sbomify.com/CVE-2017-12617/): Apache Tomcat Remote Code Execution (high 8.1, exploited in the wild)
- [CVE-2017-12615](https://insights.sbomify.com/CVE-2017-12615/): Apache Tomcat on Windows Remote Code Execution (high 8.1, exploited in the wild)
- [CVE-2026-34486](https://insights.sbomify.com/CVE-2026-34486/): Apache Tomcat Missing Encryption of Sensitive Data (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-30640 and fix it if it is affected.

What it is: CVE-2021-30640 is a medium-severity authentication bypass vulnerability in Apache Tomcat, published on 12 Jul 2021. 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-2021-30640 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.tomcat:tomcat (Maven): affected from 10.0.0-M1; fixed in 10.0.5
- org.apache.tomcat:tomcat (Maven): affected from 10.0.0-M1; fixed in 10.0.5
- org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.65
- org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.65
- org.apache.tomcat:tomcat (Maven): affected from 9.0.0M1; fixed in 9.0.45
- org.apache.tomcat:tomcat (Maven): affected from 9.0.0M1; fixed in 9.0.45
- tomcat (Bitnami): affected from 7.0.0; fixed in 7.0.109, 8.5.66, 9.0.46, 10.0.6

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-2021-30640/ (Markdown: https://insights.sbomify.com/CVE-2021-30640/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-30640
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-30640
- OSV: https://osv.dev/vulnerability/CVE-2021-30640

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-30640/
Summaries are generated and may contain mistakes; the official description above is the record.