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HIGH severity

CVE-2016-6816 — tomcat-coyote

HIGHFix: apache/tomcat@516bda6

CVE-2016-6816 is a high-severity (CVSS 7.1) Improper Input Validation vulnerability in org.apache.tomcat:tomcat-coyote. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for org.apache.tomcat:tomcat-coyote — see the affected versions and patch details below.

Improper Input Validation in Apache Tomcat

Also known asGHSA-jc7p-5r39-9477
Published
Updated
Affected
5 pkgs
Patched
5 / 5
Exploits
1 known
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2016-6816.

EPSS Exploitation Probability

via FIRST.org ↗
39.6%probability of exploitation in next 30 days
Moderate Risk0.00%
Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk
0.00%16.9%33.8%50.6%2.9%39.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

5 pkgs affected
☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

The code in Apache Tomcat 9.0.0.M1 to 9.0.0.M11, 8.5.0 to 8.5.6, 8.0.0.RC1 to 8.0.38, 7.0.0 to 7.0.72, and 6.0.0 to 6.0.47 that parsed the HTTP request line permitted invalid characters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack and/or obtain sensitive information from requests other then their own.

Affected Packages

5 total 5 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 9.0.0.M1&&< 9.0.0.M129.0.0.M12org.apache.tomcat:tomcat-coyote:9.0.0.M12
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 8.5.0&&< 8.5.88.5.8org.apache.tomcat:tomcat-coyote:8.5.8
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 8.0.0RC1&&< 8.0.398.0.39org.apache.tomcat:tomcat-coyote:8.0.39
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 7.0.0&&< 7.0.737.0.73org.apache.tomcat:tomcat-coyote:7.0.73
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 6.0.0&&< 6.0.486.0.48org.apache.tomcat:tomcat-coyote:6.0.48

Affected Products

1 product · 178 configurations
Application
tomcatapache
168 versions
6.0.06.0.16.0.26.0.36.0.46.0.56.0.66.0.76.0.86.0.96.0.106.0.11
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-41783remotemultiple

Apache Tomcat 6/7/8/9 - Information Disclosure

by justpentest · Apr 4, 2017

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat-coyote, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.tomcat:tomcat-coyote to 9.0.0.M12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-6816 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Applying the fix provided to mitigate this issue may cause Tomcat to return 400 status after updating. For more information, refer to https://access.redhat.com/solutions/2891171

ProductFixed inAdvisory
Red Hat Enterprise Linux 6tomcat6-0:6.0.24-105.el6_8RHSA-2017:0527
Red Hat Enterprise Linux 7tomcat-0:7.0.69-11.el7_3RHSA-2017:0935
Red Hat JBoss Enterprise Application Platform 6.4see advisoryRHSA-2017:0247
Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 5apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el5RHSA-2017:0246
Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 6apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el6RHSA-2017:0244
Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 6jboss-ec2-eap-0:7.5.13-1.Final_redhat_2.ep6.el6RHSA-2017:0250
Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 7apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el7RHSA-2017:0245
Red Hat JBoss Web Server 3.1see advisoryRHSA-2017:0457

Frequently Asked Questions

The code in Apache Tomcat 9.0.0.M1 to 9.0.0.M11, 8.5.0 to 8.5.6, 8.0.0.RC1 to 8.0.38, 7.0.0 to 7.0.72, and 6.0.0 to 6.0.47 that parsed the HTTP request line permitted invalid characters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack and/or obtain sensitive information from requests other then their own.
O3 Security · Impact-Aware SCA

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CVE-2016-6816: tomcat-coyote XSS — Fixed in 9.0.0.M12