CVE-2016-6816 — tomcat-coyote
HIGHCVE-2016-6816 is a high-severity (CVSS 7.1) Improper Input Validation vulnerability in org.apache.tomcat:tomcat-coyote. 1 public exploit reference exists, 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
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2016-6816 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyoteReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 9.0.0.M1&&< 9.0.0.M12 | 9.0.0.M12org.apache.tomcat:tomcat-coyote:9.0.0.M12 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 8.5.0&&< 8.5.8 | 8.5.8org.apache.tomcat:tomcat-coyote:8.5.8 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 8.0.0RC1&&< 8.0.39 | 8.0.39org.apache.tomcat:tomcat-coyote:8.0.39 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 7.0.0&&< 7.0.73 | 7.0.73org.apache.tomcat:tomcat-coyote:7.0.73 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 6.0.0&&< 6.0.48 | 6.0.48org.apache.tomcat:tomcat-coyote:6.0.48 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Apache Tomcat 6/7/8/9 - Information Disclosure
by justpentest · Apr 4, 2017
Detection & mitigation playbook
Open-source dependencyDetect
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.
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.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2016-6816 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2016-6816. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
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
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 6 | tomcat6-0:6.0.24-105.el6_8 | RHSA-2017:0527 |
| Red Hat Enterprise Linux 7 | tomcat-0:7.0.69-11.el7_3 | RHSA-2017:0935 |
| Red Hat JBoss Enterprise Application Platform 6.4 | see advisory | RHSA-2017:0247 |
| Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 5 | apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el5 | RHSA-2017:0246 |
| Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 6 | apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el6 | RHSA-2017:0244 |
| Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 6 | jboss-ec2-eap-0:7.5.13-1.Final_redhat_2.ep6.el6 | RHSA-2017:0250 |
| Red Hat JBoss Enterprise Application Platform 6.4 for RHEL 7 | apache-cxf-0:2.7.18-5.SP4_redhat_1.1.ep6.el7 | RHSA-2017:0245 |
| Red Hat JBoss Web Server 3.1 | see advisory | RHSA-2017:0457 |
Frequently Asked Questions
Is CVE-2016-6816 in your dependencies?
O3 Security finds CVE-2016-6816 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.