# CVE-2021-41079: Apache Tomcat DoS with unexpected TLS packet > Attackers can cause a denial of service via infinite loop in Apache Tomcat when using NIO+OpenSSL or NIO2+OpenSSL for TLS. - **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:** 16 Sep 2021 - **Updated:** 8 Oct 2026 - **Also known as:** BIT-tomcat-2021-41079, DEBIAN-CVE-2021-41079, DLA-2764-1, DSA-4986-1, GHSA-59g9-7gfx-c72p, OESA-2021-1393, OESA-2022-1622, RHSA-2021:3741, UBUNTU-CVE-2021-41079 ## What is CVE-2021-41079? CVE-2021-41079 is a high-severity denial of service vulnerability in Apache Tomcat, published on 16 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Apache Tomcat 8.5.0 to 8.5.63, 9.0.0-M1 to 9.0.43 and 10.0.0-M1 to 10.0.2 did not properly validate incoming TLS packets. When Tomcat was configured to use NIO+OpenSSL or NIO2+OpenSSL for TLS, a specially crafted packet could be used to trigger an infinite loop resulting in a denial of service. Weakness: CWE-835 (Loop with Unreachable Exit Condition), CWE-20 (Improper Input Validation) ## Which versions are affected by CVE-2021-41079? 7 open source packages ship an affected version, including org.apache.tomcat:tomcat and tomcat. It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.tomcat:tomcat` | Maven | From 10.0.0 | 10.0.4 | | `org.apache.tomcat:tomcat` | Maven | From 10.0.0 | 10.0.4 | | `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.64 | | `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.64 | | `org.apache.tomcat:tomcat` | Maven | From 9.0.0 | 9.0.44 | | `org.apache.tomcat:tomcat` | Maven | From 9.0.0 | 9.0.44 | | `tomcat` | Bitnami | From 8.5.0 | 8.5.64, 9.0.44, 10.0.3 | | `jws5-tomcat` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-admin-webapps` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-docs-webapp` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-el-3.0-api` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-java-jdk11` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-java-jdk8` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-javadoc` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-jsp-2.3-api` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-lib` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-selinux` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-servlet-4.0-api` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat-webapps` | Red Hat:jboss_enterprise_web_server:5.5::el7 | All versions | 0:9.0.43-13.redhat_00013.1.el7jws | | `jws5-tomcat` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-admin-webapps` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-docs-webapp` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-el-3.0-api` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-javadoc` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-jsp-2.3-api` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-lib` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-selinux` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-servlet-4.0-api` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | | `jws5-tomcat-webapps` | Red Hat:jboss_enterprise_web_server:5.5::el8 | All versions | 0:9.0.43-13.redhat_00013.1.el8jws | Products: Apache Tomcat, Debian Debian Linux, Netapp Management Services for Element Software and Netapp Hci. ## How do I fix CVE-2021-41079? Upgrade org.apache.tomcat:tomcat to a fixed version for your release line: 10.0.4, 8.5.64 or 9.0.44. ## Is CVE-2021-41079 being exploited? There is no known exploitation of CVE-2021-41079 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-2021-41079 and fix it if it is affected. What it is: CVE-2021-41079 is a high-severity denial of service vulnerability in Apache Tomcat, published on 16 Sep 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-2021-41079 in the wild and no public exploit code. Affected packages and fixed versions: - org.apache.tomcat:tomcat (Maven): affected from 10.0.0; fixed in 10.0.4 - org.apache.tomcat:tomcat (Maven): affected from 10.0.0; fixed in 10.0.4 - org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.64 - org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.64 - org.apache.tomcat:tomcat (Maven): affected from 9.0.0; fixed in 9.0.44 - org.apache.tomcat:tomcat (Maven): affected from 9.0.0; fixed in 9.0.44 - tomcat (Bitnami): affected from 8.5.0; fixed in 8.5.64, 9.0.44, 10.0.3 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-2021-41079/ (Markdown: https://insights.sbomify.com/CVE-2021-41079/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41079 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41079 - OSV: https://osv.dev/vulnerability/CVE-2021-41079 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-41079/ Summaries are generated and may contain mistakes; the official description above is the record.