# CVE-2021-25122: Apache Tomcat h2c request mix-up > Apache Tomcat may leak request headers and body data between users during h2c connection handling, allowing one user to see another's request details. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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:** 1 Mar 2021 - **Updated:** 8 Oct 2026 - **Also known as:** BIT-tomcat-2021-25122, DEBIAN-CVE-2021-25122, GHSA-j39c-c8hj-x4j3, ROOT-APP-MAVEN-CVE-2021-25122, UBUNTU-CVE-2021-25122 ## What is CVE-2021-25122? CVE-2021-25122 is a high-severity vulnerability in Apache Tomcat, published on 1 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description When responding to new h2c connection requests, Apache Tomcat versions 10.0.0-M1 to 10.0.0, 9.0.0.M1 to 9.0.41 and 8.5.0 to 8.5.61 could duplicate request headers and a limited amount of request body from one request to another meaning user A and user B could both see the results of user A's request. Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) ## Which versions are affected by CVE-2021-25122? 9 open source packages ship an affected version, including org.apache.tomcat.embed:tomcat-embed-core, tomcat and org.apache.tomcat:tomcat-coyote. It affects 12 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 10.0.0-M1 | 10.0.2 | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 10.0.0-M1 | 10.0.2 | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 8.5.0 | 8.5.63 | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 8.5.0 | 8.5.63 | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 9.0.0-M1 | 9.0.43 | | `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 9.0.0-M1 | 9.0.43 | | `tomcat` | Bitnami | From 8.5.0 | 8.5.62, 9.0.42, 10.0.1 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 10.0.0-M1 | 10.0.2 | | `org.apache.tomcat:tomcat-coyote` | Maven | From 10.0.0-M1 | 10.0.2 | Products: Apache Tomcat, Debian Debian Linux, Oracle Agile Product Lifecycle Management, Oracle Communications Cloud Native Core Policy, Oracle Communications Cloud Native Core Security Edge Protection Proxy, Oracle Communications Instant Messaging Server, Oracle Database, Oracle Graph Server and Client, Oracle Instantis Enterprisetrack, Oracle Managed File Transfer, Oracle Mysql Enterprise Monitor, Oracle Siebel Ui Framework. ## How do I fix CVE-2021-25122? Upgrade org.apache.tomcat.embed:tomcat-embed-core to a fixed version for your release line: 10.0.2, 8.5.63 or 9.0.43. ## Is CVE-2021-25122 being exploited? There is no known exploitation of CVE-2021-25122 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-2021-25122 and fix it if it is affected. What it is: CVE-2021-25122 is a high-severity vulnerability in Apache Tomcat, published on 1 Mar 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-2021-25122 in the wild and no public exploit code. Affected packages and fixed versions: - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 10.0.0-M1; fixed in 10.0.2 - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 10.0.0-M1; fixed in 10.0.2 - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 8.5.0; fixed in 8.5.63 - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 8.5.0; fixed in 8.5.63 - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 9.0.0-M1; fixed in 9.0.43 - org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 9.0.0-M1; fixed in 9.0.43 - tomcat (Bitnami): affected from 8.5.0; fixed in 8.5.62, 9.0.42, 10.0.1 - org.apache.tomcat:tomcat-coyote (Maven): affected from 10.0.0-M1; fixed in 10.0.2 - org.apache.tomcat:tomcat-coyote (Maven): affected from 10.0.0-M1; fixed in 10.0.2 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-2021-25122/ (Markdown: https://insights.sbomify.com/CVE-2021-25122/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25122 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25122 - OSV: https://osv.dev/vulnerability/CVE-2021-25122 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-25122/ Summaries are generated and may contain mistakes; the official description above is the record.