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AUSCERT External Security Bulletin Redistribution
ESB-2020.0667
Apache Tomcat Vulnerabilities
25 February 2020
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AusCERT Security Bulletin Summary
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Product: Tomcat
Publisher: Apache
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Provide Misleading Information -- Remote/Unauthenticated
Access Confidential Data -- Remote/Unauthenticated
Unauthorised Access -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-1938 CVE-2020-1935 CVE-2019-17569
Original Bulletin:
https://www.mail-archive.com/users@tomcat.apache.org/msg134240.html
https://www.mail-archive.com/users@tomcat.apache.org/msg134239.html
https://www.mail-archive.com/users@tomcat.apache.org/msg134241.html
Comment: This bulletin contains three (3) Apache security advisories.
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CVE-2020-1938 AJP Request Injection and potential Remote Code Execution
Severity: High
Vendor: The Apache Software Foundation
Versions Affected:
Apache Tomcat 9.0.0.M1 to 9.0.30
Apache Tomcat 8.5.0 to 8.5.50
Apache Tomcat 7.0.0 to 7.0.99
Description:
When using the Apache JServ Protocol (AJP), care must be taken when
trusting incoming connections to Apache Tomcat. Tomcat treats AJP
connections as having higher trust than, for example, a similar HTTP
connection. If such connections are available to an attacker, they can
be exploited in ways that may be surprising.
Prior to Tomcat 9.0.31, 8.5.51 and 7.0.100, Tomcat shipped with an AJP
Connector enabled by default that listened on all configured IP
addresses. It was expected (and recommended in the security guide) that
this Connector would be disabled if not required.
Prior to this vulnerability report, the known risks of an attacker being
able to access the AJP port directly were:
- - bypassing security checks based on client IP address
- - bypassing user authentication if Tomcat was configured to trust
authentication data provided by the reverse proxy
This vulnerability report identified a mechanism that allowed the following:
- - returning arbitrary files from anywhere in the web application
including under the WEB-INF and META-INF directories or any other
location reachable via ServletContext.getResourceAsStream()
- - processing any file in the web application as a JSP
Further, if the web application allowed file upload and stored those
files within the web application (or the attacker was able to control
the content of the web application by some other means) then this, along
with the ability to process a file as a JSP, made remote code execution
possible.
Mitigation:
It is important to note that mitigation is only required if an AJP port
is accessible to untrusted users.
- - If AJP support is not required, the Connector may be disabled e.g. by
removing the AJP Connector element from the server.xml file
- - If AJP support is required, untrusted users may be prevented from
accessing the AJP port by one or more of the following means:
- configuring appropriate network firewall rules
- configuring an explicit address attribute to the connector so that
the Connector listens on a non-public interface
- configuring a shared secret for the AJP connection
Users wishing to take a defence-in-depth approach and block the vector
that permits returning arbitrary files and execution as JSP may upgrade to:
- - Apache Tomcat 9.0.31 or later
- - Apache Tomcat 8.5.51 or later
- - Apache Tomcat 7.0.100 or later
Users should note that a number of changes were made to the default AJP
Connector configuration in these versions to harden the default
configuration. The changes are:
- - The AJP Connector is commented out in the provided server.xml file.
- - The "requiredSecret" attribute has been renamed "secret" (the old name
continues to work but is deprecated).
- - A new attribute "secretRequired" has been added which defaults to
"true". When this attribute is "true", the AJP Connector will not
start unless a shared secret has been configured.
- - The default listen address for the AJP Connector is now the loopback
address.
It is likely that users upgrading to 9.0.31, 8.5.51 or 7.0.100 and later
will need to make small changes to their configurations as a result.
References:
[1] http://tomcat.apache.org/security-9.html
[2] http://tomcat.apache.org/security-8.html
[3] http://tomcat.apache.org/security-7.html
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CVE-2020-1935 HTTP Request Smuggling
Severity: Low
Vendor: The Apache Software Foundation
Versions Affected:
Apache Tomcat 9.0.0.M1 to 9.0.30
Apache Tomcat 8.5.0 to 8.5.50
Apache Tomcat 7.0.0 to 7.0.99
Description:
The HTTP header parsing code used an approach to end-of-line parsing
that allowed some invalid HTTP headers to be parsed as valid. This led
to a possibility of HTTP Request Smuggling if Tomcat was located behind
a reverse proxy that incorrectly handled the invalid Transfer-Encoding
header in a particular manner. Such a reverse proxy is considered unlikely.
Mitigation:
- - Upgrade to Apache Tomcat 9.0.31 or later
- - Upgrade to Apache Tomcat 8.5.51 or later
- - Upgrade to Apache Tomcat 7.0.100 or later
Credit:
This issue was found by @ZeddYu and reported responsibly to the Apache
Tomcat Security Team.
References:
[1] http://tomcat.apache.org/security-9.html
[2] http://tomcat.apache.org/security-8.html
[3] http://tomcat.apache.org/security-7.html
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CVE-2019-17569 HTTP Request Smuggling
Severity: Low
Vendor: The Apache Software Foundation
Versions Affected:
Apache Tomcat 9.0.28 to 9.0.30
Apache Tomcat 8.5.48 to 8.5.50
Apache Tomcat 7.0.98 to 7.0.99
Description:
The refactoring in 9.0.28, 8.5.48 and 7.0.98 introduced a regression.
The result of the regression was that invalid Transfer-Encoding headers
were incorrectly processed leading to a possibility of HTTP Request
Smuggling if Tomcat was located behind a reverse proxy that incorrectly
handled the invalid Transfer-Encoding header in a particular manner.
Such a reverse proxy is considered unlikely.
Mitigation:
- - Upgrade to Apache Tomcat 9.0.31 or later
- - Upgrade to Apache Tomcat 8.5.51 or later
- - Upgrade to Apache Tomcat 7.0.100 or later
Credit:
This issue was found by @ZeddYu and reported responsibly to the Apache
Tomcat Security Team.
References:
[1] http://tomcat.apache.org/security-9.html
[2] http://tomcat.apache.org/security-8.html
[3] http://tomcat.apache.org/security-7.html
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