# CVE-2021-43980: Apache Tomcat: Information disclosure > A concurrency bug in Apache Tomcat allows attackers to receive responses intended for other clients, leading to information disclosure. - **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/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:** 28 Sep 2022 - **Updated:** 21 May 2025 - **Also known as:** BIT-tomcat-2021-43980, DEBIAN-CVE-2021-43980, GHSA-jx7c-7mj5-9438, SUSE-SU-2022:4009-1, UBUNTU-CVE-2021-43980 ## What is CVE-2021-43980? CVE-2021-43980 is a low-severity vulnerability in Apache Tomcat, published on 28 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description The simplified implementation of blocking reads and writes introduced in Tomcat 10 and back-ported to Tomcat 9.0.47 onwards exposed a long standing (but extremely hard to trigger) concurrency bug in Apache Tomcat 10.1.0 to 10.1.0-M12, 10.0.0-M1 to 10.0.18, 9.0.0-M1 to 9.0.60 and 8.5.0 to 8.5.77 that could cause client connections to share an Http11Processor instance resulting in responses, or part responses, to be received by the wrong client. Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) ## Which versions are affected by CVE-2021-43980? 9 open source packages ship an affected version, including org.apache.tomcat:tomcat and tomcat. It affects 2 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.tomcat:tomcat` | Maven | From 10.0.0-M1 | 10.0.20 | | `org.apache.tomcat:tomcat` | Maven | From 10.0.0-M1 | 10.0.20 | | `org.apache.tomcat:tomcat` | Maven | From 10.1.0-M1 | 10.1.0-M14 | | `org.apache.tomcat:tomcat` | Maven | From 10.1.0-M1 | 10.1.0-M14 | | `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.78 | | `org.apache.tomcat:tomcat` | Maven | From 8.5.0 | 8.5.78 | | `org.apache.tomcat:tomcat` | Maven | From 9.0.0-M1 | 9.0.62 | | `org.apache.tomcat:tomcat` | Maven | From 9.0.0-M1 | 9.0.62 | | `tomcat` | Bitnami | From 8.5.0 | 8.5.78, 9.0.61, 10.0.19 | | `tomcat` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 9.0.36-3.90.1 | | `tomcat` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 9.0.36-3.90.1 | Products: Apache Tomcat, Debian Debian Linux. ## How do I fix CVE-2021-43980? Upgrade org.apache.tomcat:tomcat to a fixed version for your release line: 10.0.20, 10.1.0-M14, 8.5.78 or 9.0.62. ## Is CVE-2021-43980 being exploited? There is no known exploitation of CVE-2021-43980 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-2021-43980 and fix it if it is affected. What it is: CVE-2021-43980 is a low-severity vulnerability in Apache Tomcat, published on 28 Sep 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-2021-43980 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 10.0.20 - org.apache.tomcat:tomcat (Maven): affected from 10.0.0-M1; fixed in 10.0.20 - org.apache.tomcat:tomcat (Maven): affected from 10.1.0-M1; fixed in 10.1.0-M14 - org.apache.tomcat:tomcat (Maven): affected from 10.1.0-M1; fixed in 10.1.0-M14 - org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.78 - org.apache.tomcat:tomcat (Maven): affected from 8.5.0; fixed in 8.5.78 - org.apache.tomcat:tomcat (Maven): affected from 9.0.0-M1; fixed in 9.0.62 - org.apache.tomcat:tomcat (Maven): affected from 9.0.0-M1; fixed in 9.0.62 - tomcat (Bitnami): affected from 8.5.0; fixed in 8.5.78, 9.0.61, 10.0.19 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-2021-43980/ (Markdown: https://insights.sbomify.com/CVE-2021-43980/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43980 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43980 - OSV: https://osv.dev/vulnerability/CVE-2021-43980 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-43980/ Summaries are generated and may contain mistakes; the official description above is the record.