# CVE-2020-13943: Exposure of Sensitive Information to an Unauthorized Actor in Apache Tomcat > An attacker can cause users to see responses for unexpected resources by violating HTTP/2 stream limits, leading to information disclosure. - **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 12 Oct 2020 - **Updated:** 8 Oct 2026 - **Also known as:** BIT-tomcat-2020-13943, DEBIAN-CVE-2020-13943, DLA-2407-1, GHSA-f268-65qc-98vg, MGASA-2020-0397, SUSE-SU-2020:2996-1, SUSE-SU-2020:3068-1, SUSE-SU-2020:3069-1, openSUSE-SU-2020:1799-1, openSUSE-SU-2020:1842-1 ## What is CVE-2020-13943? CVE-2020-13943 is a medium-severity vulnerability in Apache Tomcat, published on 12 Oct 2020. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 exceeded the agreed maximum number of concurrent streams for a connection (in violation of the HTTP/2 protocol), it was possible that a subsequent request made on that connection could contain HTTP headers - including HTTP/2 pseudo headers - from a previous request rather than the intended headers. This could lead to users seeing responses for unexpected resources. ## Which versions are affected by CVE-2020-13943? 7 open source packages ship an affected version, including org.apache.tomcat:tomcat-coyote and tomcat. It affects 4 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.tomcat:tomcat-coyote` | Maven | From 10.0.0-M1 | 10.0.0-M8 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 10.0.0-M1 | 10.0.0-M8 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 8.5.0 | 8.5.58 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 8.5.0 | 8.5.58 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 9.0.0-M1 | 9.0.38 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 9.0.0-M1 | 9.0.38 | | `tomcat` | Bitnami | From 8.5.0 | 8.5.1, 8.5.2, 8.5.3, 8.5.4, 8.5.5, 8.5.6, 8.5.7, 8.5.8, 8.5.9, 8.5.10, 8.5.11, 8.5.12, 8.5.13, 8.5.14, 8.5.15, 8.5.16, 8.5.17, 8.5.18, 8.5.19, 8.5.20, 8.5.21, 8.5.22, 8.5.23, 8.5.24, 8.5.25, 8.5.26, 8.5.27, 8.5.28, 8.5.29, 8.5.30, 8.5.31, 8.5.32, 8.5.33, 8.5.34, 8.5.35, 8.5.36, 8.5.37, 8.5.38, 8.5.39, 8.5.40, 8.5.41, 8.5.42, 8.5.43, 8.5.44, 8.5.45, 8.5.46, 8.5.47, 8.5.48, 8.5.49, 8.5.50, 8.5.51, 8.5.52, 8.5.53, 8.5.54, 8.5.55, 8.5.56, 8.5.57, 8.5.58, 9.0.38 | | `tomcat` | SUSE:Linux Enterprise Module for Web and Scripting 15 SP1 | All versions | 9.0.36-4.47.3 | | `tomcat` | SUSE:Linux Enterprise Module for Web and Scripting 15 SP2 | All versions | 9.0.36-3.12.3 | | `tomcat` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 9.0.36-3.50.1 | | `tomcat` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 9.0.36-3.50.1 | | `tomcat` | openSUSE:Leap 15.1 | All versions | 9.0.36-lp151.3.33.1 | | `tomcat` | openSUSE:Leap 15.2 | All versions | 9.0.36-lp152.2.10.1 | Products: Apache Tomcat, Debian Debian Linux, Oracle Instantis Enterprisetrack, Oracle Sd-Wan Edge. ## How do I fix CVE-2020-13943? Upgrade org.apache.tomcat:tomcat-coyote to a fixed version for your release line: 10.0.0-M8, 8.5.58 or 9.0.38. ## Is CVE-2020-13943 being exploited? There is no known exploitation of CVE-2020-13943 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-2020-13943 and fix it if it is affected. What it is: CVE-2020-13943 is a medium-severity vulnerability in Apache Tomcat, published on 12 Oct 2020. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2020-13943 in the wild and no public exploit code. Affected packages and fixed versions: - org.apache.tomcat:tomcat-coyote (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M8 - org.apache.tomcat:tomcat-coyote (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M8 - org.apache.tomcat:tomcat-coyote (Maven): affected from 8.5.0; fixed in 8.5.58 - org.apache.tomcat:tomcat-coyote (Maven): affected from 8.5.0; fixed in 8.5.58 - org.apache.tomcat:tomcat-coyote (Maven): affected from 9.0.0-M1; fixed in 9.0.38 - org.apache.tomcat:tomcat-coyote (Maven): affected from 9.0.0-M1; fixed in 9.0.38 - tomcat (Bitnami): affected from 8.5.0; fixed in 8.5.1, 8.5.2, 8.5.3, 8.5.4, 8.5.5, 8.5.6, 8.5.7, 8.5.8, 8.5.9, 8.5.10, 8.5.11, 8.5.12, 8.5.13, 8.5.14, 8.5.15, 8.5.16, 8.5.17, 8.5.18, 8.5.19, 8.5.20, 8.5.21, 8.5.22, 8.5.23, 8.5.24, 8.5.25, 8.5.26, 8.5.27, 8.5.28, 8.5.29, 8.5.30, 8.5.31, 8.5.32, 8.5.33, 8.5.34, 8.5.35, 8.5.36, 8.5.37, 8.5.38, 8.5.39, 8.5.40, 8.5.41, 8.5.42, 8.5.43, 8.5.44, 8.5.45, 8.5.46, 8.5.47, 8.5.48, 8.5.49, 8.5.50, 8.5.51, 8.5.52, 8.5.53, 8.5.54, 8.5.55, 8.5.56, 8.5.57, 8.5.58, 9.0.38 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-2020-13943/ (Markdown: https://insights.sbomify.com/CVE-2020-13943/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-13943 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-13943 - OSV: https://osv.dev/vulnerability/CVE-2020-13943 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-13943/ Summaries are generated and may contain mistakes; the official description above is the record.