CVE-2016-6816

HIGHEPSS 99th pctl

7.1

CVSS v3

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.

CWE-20Improper Input Validation

How to fix

Remediation Available

libservlet2.5-javaUbuntu

Fixed in:6.0.45+dfsg-1ubuntu0.1USN-4557-1

libtomcat7-javaUbuntu

Fixed in:7.0.52-1ubuntu0.8USN-3177-1

libtomcat8-javaUbuntu

Fixed in:8.0.32-1ubuntu1.3USN-3177-1

tomcat6Ubuntu

Fixed in:6.0.45+dfsg-1ubuntu0.1USN-4557-1

tomcat7Ubuntu

Fixed in:7.0.52-1ubuntu0.8USN-3177-1

tomcat8Ubuntu

Fixed in:8.0.32-1ubuntu1.3USN-3177-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityLow

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L

Exploit Intelligence

39.63%probability of exploitation in 30 days

99thpercentile

Very high risk: more likely to be exploited than 99% of all known CVEs.

References

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix

Common questions

How do I fix CVE-2016-6816?

Published advisories record a fix for 6 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2016-6816 being actively exploited?

Not that we know of. CVE-2016-6816 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 39.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 99% of all scored CVEs.

How severe is CVE-2016-6816?

CVE-2016-6816 has a CVSS v3 base score of 7.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2016-6816 affect?

Published advisories record a fix for libservlet2.5-java (Ubuntu), libtomcat7-java (Ubuntu), libtomcat8-java (Ubuntu), tomcat6 (Ubuntu), and 2 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-13.