# CVE-2016-8745: Concurrent Execution using Shared Resource with Improper Synchronization in Apache Tomcat > An attacker can exploit a concurrency bug in the NIO connector to leak sensitive data like session IDs and response bodies between requests. - **Severity:** High 7.5 (`CVSS:3.0/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:** 10 Aug 2017 - **Updated:** 14 Nov 2024 - **Also known as:** DLA-779-1, DSA-3754-1, DSA-3755-1, GHSA-w3j5-q8f2-3cqq, MGASA-2017-0050, UBUNTU-CVE-2016-8745 ## What is CVE-2016-8745? CVE-2016-8745 is a high-severity vulnerability in Apache Tomcat, published on 10 Aug 2017. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description A bug in the error handling of the send file code for the NIO HTTP connector in Apache Tomcat 9.0.0.M1 to 9.0.0.M13, 8.5.0 to 8.5.8, 8.0.0.RC1 to 8.0.39, 7.0.0 to 7.0.73 and 6.0.16 to 6.0.48 resulted in the current Processor object being added to the Processor cache multiple times. This in turn meant that the same Processor could be used for concurrent requests. Sharing a Processor can result in information leakage between requests including, not not limited to, session ID and the response body. The bug was first noticed in 8.5.x onwards where it appears the refactoring of the Connector code for 8.5.x onwards made it more likely that the bug was observed. Initially it was thought that the 8.5.x refactoring introduced the bug but further investigation has shown that the bug is present in all currently supported Tomcat versions. Weakness: CWE-388 ## Which versions are affected by CVE-2016-8745? 10 open source packages ship an affected version, including org.apache.tomcat:tomcat-util. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.apache.tomcat:tomcat-util` | Maven | From 6.0.16 | 6.0.50 | | `org.apache.tomcat:tomcat-util` | Maven | From 6.0.16 | 6.0.50 | | `org.apache.tomcat:tomcat-util` | Maven | From 7.0.0 | 7.0.75 | | `org.apache.tomcat:tomcat-util` | Maven | From 7.0.0 | 7.0.75 | | `org.apache.tomcat:tomcat-util` | Maven | From 8.0.0-RC1 | 8.0.41 | | `org.apache.tomcat:tomcat-util` | Maven | From 8.0.0-RC1 | 8.0.41 | | `org.apache.tomcat:tomcat-util` | Maven | From 8.5.0 | 8.5.9 | | `org.apache.tomcat:tomcat-util` | Maven | From 8.5.0 | 8.5.9 | | `org.apache.tomcat:tomcat-util` | Maven | From 9.0.0.M1 | 9.0.0.M14 | | `org.apache.tomcat:tomcat-util` | Maven | From 9.0.0.M1 | 9.0.0.M14 | Products: Apache Tomcat. ## How do I fix CVE-2016-8745? Upgrade org.apache.tomcat:tomcat-util to a fixed version for your release line: 6.0.50, 7.0.75, 8.0.41 or 8.5.9. ## Is CVE-2016-8745 being exploited? There is no known exploitation of CVE-2016-8745 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-2016-8745 and fix it if it is affected. What it is: CVE-2016-8745 is a high-severity vulnerability in Apache Tomcat, published on 10 Aug 2017. 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-2016-8745 in the wild and no public exploit code. Affected packages and fixed versions: - org.apache.tomcat:tomcat-util (Maven): affected from 6.0.16; fixed in 6.0.50 - org.apache.tomcat:tomcat-util (Maven): affected from 6.0.16; fixed in 6.0.50 - org.apache.tomcat:tomcat-util (Maven): affected from 7.0.0; fixed in 7.0.75 - org.apache.tomcat:tomcat-util (Maven): affected from 7.0.0; fixed in 7.0.75 - org.apache.tomcat:tomcat-util (Maven): affected from 8.0.0-RC1; fixed in 8.0.41 - org.apache.tomcat:tomcat-util (Maven): affected from 8.0.0-RC1; fixed in 8.0.41 - org.apache.tomcat:tomcat-util (Maven): affected from 8.5.0; fixed in 8.5.9 - org.apache.tomcat:tomcat-util (Maven): affected from 8.5.0; fixed in 8.5.9 - org.apache.tomcat:tomcat-util (Maven): affected from 9.0.0.M1; fixed in 9.0.0.M14 - org.apache.tomcat:tomcat-util (Maven): affected from 9.0.0.M1; fixed in 9.0.0.M14 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-2016-8745/ (Markdown: https://insights.sbomify.com/CVE-2016-8745/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2016-8745 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-8745 - OSV: https://osv.dev/vulnerability/CVE-2016-8745 --- From sbomify Insights: https://insights.sbomify.com/CVE-2016-8745/ Summaries are generated and may contain mistakes; the official description above is the record.