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AUSCERT External Security Bulletin Redistribution
ESB-2019.4305.3
TMM vulnerability CVE-2019-6660
10 January 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: F5 BIG-IP products
Publisher: F5 Networks
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2019-6660
Original Bulletin:
https://support.f5.com/csp/article/K23860356
Revision History: January 10 2020: Vendor provided additional mitigation
instructions.
November 22 2019: Clarified the Security Advisory Description
section
November 15 2019: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
K23860356: TMM vulnerability CVE-2019-6660
Original Publication Date: 15 Nov, 2019
Latest Publication Date: 08 Jan, 2020
Security Advisory Description
iRules performing HTTP header manipulation may cause a denial-of-service(DoS)
when processing traffic handled by a virtual server with an associated HTTP
profile, in specific circumstances, when the requests do not strictly conform
to RFCs.(CVE-2019-6660)
Impact
The affected BIG-IP system's Traffic Management Microkernel (TMM) process
enters a loop when handling malformed HTTP requests, and this may result in an
interruption in traffic processing. If the BIG-IP system is part of a high
availability (HA) group, a device failover may occur.
Security Advisory Status
F5 Product Development has assigned ID 767653 (BIG-IP) to this vulnerability.
To determine if your product and version have been evaluated for this
vulnerability, refer to the Applies to (see versions) box. To determine if your
release is known to be vulnerable, the components or features that are affected
by the vulnerability, and for information about releases, point releases, or
hotfixes that address the vulnerability, refer to the following table. For more
information about security advisory versioning, refer to K51812227:
Understanding Security Advisory versioning.
+-------------------+------+----------+----------+----------+------+----------+
| | |Versions |Fixes | |CVSSv3|Vulnerable|
|Product |Branch|known to |introduced|Severity |score^|component |
| | |be |in | |1 |or feature|
| | |vulnerable| | | | |
+-------------------+------+----------+----------+----------+------+----------+
| |15.x |None |15.0.0 | | | |
| +------+----------+----------+ | | |
| | |14.1.0 - | | | | |
| |14.x |14.1.2 |14.1.2.1 | | | |
|BIG-IP (LTM, AAM, | |14.0.0 - |14.0.1.1 | | | |
|AFM, Analytics, | |14.0.1 | | | | |
|APM, ASM, DNS, Edge+------+----------+----------+ | | |
|Gateway, FPS, GTM, |13.x |13.1.0 - |13.1.3 |High |7.5 |TMM |
|Link Controller, | |13.1.1 | | | | |
|PEM, +------+----------+----------+ | | |
|WebAccelerator) |12.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
| |11.x |None |Not | | | |
| | | |applicable| | | |
+-------------------+------+----------+----------+----------+------+----------+
|Enterprise Manager |3.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+-------------------+------+----------+----------+----------+------+----------+
| |7.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
|BIG-IQ Centralized |6.x |None |Not |Not |None |None |
|Management | | |applicable|vulnerable| | |
| +------+----------+----------+ | | |
| |5.x |None |Not | | | |
| | | |applicable| | | |
+-------------------+------+----------+----------+----------+------+----------+
|F5 iWorkflow |2.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+-------------------+------+----------+----------+----------+------+----------+
|Traffix SDC |5.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+-------------------+------+----------+----------+----------+------+----------+
^1The CVSSv3 score link takes you to a resource outside of AskF5, and it is
possible that the document may be removed without our knowledge.
Security Advisory Recommended Actions
If you are running a version listed in the Versions known to be vulnerable
column, you can eliminate this vulnerability by upgrading to a version listed
in the Fixes introduced in column. If the table lists only an older version
than what you are currently running, or does not list a non-vulnerable version,
then no upgrade candidate currently exists.
Mitigation
To mitigate this vulnerability, you can modify any iRule that performs HTTP
header manipulation on the affected virtual server, to stop processing when the
system detects an HTTP request that uses version HTTP/0.9.
An example of an iRules statement that detects and stops the processing of an
HTTP request that uses version HTTP/0.9 may appear as follows:
if {[HTTP::version] equals "0.9"} {return}
For the mitigation to be effective, you have to:
1. Use the iRules statement in existing iRules that preform HTTP header
manipulation.
2. Insert the iRules statement at the top of HTTP iRule events.
You can insert the statement into an existing iRule that handles HTTP requests
for the affected virtual server.
For example, take the following rule:
ltm rule /Common/My_Existing_iRule {
when HTTP_REQUEST {
#<Existing iRule statements>
}
}
Insert the statement if {[HTTP::version] equals "0.9"} {return} at the top of
the HTTP event:
ltm rule /Common/My_Existing_iRule {
when HTTP_REQUEST {
if {[HTTP::version] equals "0.9"} {return}
#<Existing iRule statements>
}
}
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