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AUSCERT External Security Bulletin Redistribution
ESB-2022.0500.2
K05295469: Expat vulnerability CVE-2019-15903
26 April 2022
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: BIG-IP (all modules)
BIG-IQ Centralized Management
F5OS-C
Traffix SDC
Publisher: F5 Networks
Operating System: Network Appliance
Resolution: Patch/Upgrade
CVE Names: CVE-2019-15903
Reference: ESB-2021.4058
ESB-2021.2657
Original Bulletin:
https://support.f5.com/csp/article/K05295469
Comment: CVSS (Max): 7.5 CVE-2019-15903 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVSS Source: F5 Networks
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Revision History: April 26 2022: Significant mitigation details added by vendor
February 4 2022: Initial Release
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K05295469: Expat vulnerability CVE-2019-15903
Original Publication Date: 04 Feb, 2022
Latest Publication Date: 23 Apr, 2022
Security Advisory Description
In libexpat before 2.2.8, crafted XML input could fool the parser into changing
from DTD parsing to document parsing too early; a consecutive call to
XML_GetCurrentLineNumber (or XML_GetCurrentColumnNumber) then resulted in a
heap-based buffer over-read. (CVE-2019-15903)
Impact
A remote attacker could send specially crafted XML which, when parsed by an
application using the Expat library, would result in a buffer over-read and
cause the application to stop responding.
Security Advisory Status
F5 Product Development has assigned ID 1028497 (BIG-IP), ID 1028497-8 (BIG-IQ),
SDC-1663, SDC-1662 (Traffix SDC), and ID 1073089 F5OS to this vulnerability.
This issue has been classified as CWE-749: Exposed Dangerous Method or Function
.
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.
Note: After a fix is introduced for a given minor branch, that fix applies to
all subsequent maintenance and point releases for that branch, and no
additional fixes for that branch will be listed in the table. For example, when
a fix is introduced in 14.1.2.3, the fix also applies to 14.1.2.4, and all
later 14.1.x releases (14.1.3.x., 14.1.4.x). For more information, refer to
K51812227: Understanding security advisory versioning. Additionally, software
versions preceding those listed in the Applies to (see versions) box of this
article have reached the End of Technical Support (EoTS) phase of their
lifecycle and are no longer evaluated for security issues. For more
information, refer to the Security hotfixes section of K4602: Overview of the
F5 security vulnerability response policy.
+------------+------+--------------+----------+----------+------+-------------+
| | |Versions known|Fixes | |CVSSv3|Vulnerable |
|Product |Branch|to be |introduced|Severity |score^|component or |
| | |vulnerable^1 |in | |2 |feature |
+------------+------+--------------+----------+----------+------+-------------+
| |16.x |16.1.0 - |16.1.2 | | | |
| | |16.1.1 | | | | |
| +------+--------------+----------+ | | |
| |15.x |15.1.0 - |15.1.4.1 | | | |
| | |15.1.4 | | | | |
| +------+--------------+----------+ | | |
| |14.x |14.1.0 - |14.1.4.5 | | | |
|BIG-IP (all | |14.1.4 | | | |Expat library|
|modules) +------+--------------+----------+High |7.5 |^3 |
| |13.x |13.1.0 - |13.1.5 | | | |
| | |13.1.4 | | | | |
| +------+--------------+----------+ | | |
| |12.x |12.1.0 - |Will not | | | |
| | |12.1.6 |fix | | | |
| +------+--------------+----------+ | | |
| |11.x |11.6.1 - |Will not | | | |
| | |11.6.5 |fix | | | |
+------------+------+--------------+----------+----------+------+-------------+
|BIG-IQ |8.x |8.0.0 - 8.1.0 |None | | |Expat library|
|Centralized +------+--------------+----------+High |7.5 |^3 |
|Management |7.x |7.0.0 - 7.1.0 |None | | | |
+------------+------+--------------+----------+----------+------+-------------+
|F5OS-A |1.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+------------+------+--------------+----------+----------+------+-------------+
|F5OS-C |1.x |1.2.0 - 1.3.1 |None |High |7.5 |Expat library|
| | |1.1.0 - 1.1.4 | | | |^3 |
+------------+------+--------------+----------+----------+------+-------------+
|Traffix SDC |5.x |5.2.0 |None |High |7.5 |Expat library|
| | |5.1.0 | | | | |
+------------+------+--------------+----------+----------+------+-------------+
^1F5 evaluates only software versions that have not yet reached the End of
Technical Support (EoTS) phase of their lifecycle.
^2The CVSSv3 score link takes you to a resource outside of AskF5, and it is
possible that the document may be removed without our knowledge.
^3Expat is actively used by the BIG-IP control plane (CLI and Configuration
utility), iControl SOAP API, BIG-IP ASM, BIG-IP DNS, and BIG-IP GTM, only by
authenticated users.
BIG-IP DNS, BIG-IP GTM, and BIG-IQ use Expat in the synchronization and iQuery
communication between devices, over an encrypted and authenticated channel.
F5OS and VELOS use Expat when communicating with the F5 licensing server.
Custom health monitors can include XML output, which could be parsed using
Expat, if configured to do so.
Recommended Actions
If you are running a version listed in the Versions known to be vulnerable
column, you can eliminate this vulnerability by installing a version listed in
the Fixes introduced in column. If the Fixes introduced in column does not list
a version for your branch, then no update candidate currently exists for that
branch and F5 recommends upgrading to a version with the fix (refer to the
table).
If the Fixes introduced in column lists a version prior to the one you are
running, in the same branch, then your version should have the fix.
Mitigation
Until you can install a fixed version, you can use the following sections as
temporary mitigations. These mitigations restrict access to the BIG-IP or
BIG-IQ Configuration utility, command line through SSH, and port 4353 for
iQuery communication to only trusted networks or devices, thereby limiting the
attack surface.
o Block Configuration utility, SSH, and port 4353 access through self IP
addresses
o Block Configuration utility, SSH, and port 4353 access through the
management interface
Block Configuration utility, SSH, and port 4353 access through self IP
addresses
You can block all access to the Configuration utility SSH of your BIG-IP or
BIG-IQ system using self IP addresses. To do so, you can change the Port
Lockdown setting to Allow None for each self IP address on the system. If you
must open any ports, you should use the Allow Custom option, taking care to
block access to the Configuration utility, SSH, and 4353. By default, the
Configuration utility listens on TCP port 443 and the SSH service listens on
TCP port 22. If you modified the default port, ensure that you block access to
the alternate port you configured.
Note: Performing this action prevents all access to the Configuration utility,
iControl REST, SSH, and to port 4353 using the self IP address. These changes
may also impact other services, including breaking high availability (HA)
configurations and iQuery communication.
Before you make changes to the configuration of your self IP addresses, F5
strongly recommends that you refer to the following articles:
o K17333: Overview of port lockdown behavior (12.x - 16.x)
o K39403510: Managing the port lockdown configuration on the BIG-IQ system
o K13092: Overview of securing access to the BIG-IP system
o K31003634: The Configuration utility of the Single-NIC BIG-IP Virtual
Edition now defaults to TCP port 8443
o K51358480: The single-NIC BIG-IP VE may erroneously revert to the default
management httpd port after a configuration reload
If you must expose port 443, port 22, or port 4353 on your self IP addresses
and want to restrict access to specific IP ranges, you may consider using the
packet filtering functionality built into the BIG-IP system. For more
information, refer to the following article:
o K13383: Configuring CIDR Network Addresses for the BIG-IP packet filter
Block Configuration utility, SSH, and port 4353 access through the management
interface
To mitigate this vulnerability for affected F5 products, you should restrict
management access to only trusted users and devices to F5 products over a
secure network. For more information about securing access to BIG-IP and BIG-IQ
systems, refer to the following articles:
o K13309: Restricting access to the Configuration utility by source IP
address (11.x - 16.x)
o K31401771: Restricting access to the BIG-IQ or F5 iWorkflow user interface
by source IP address
o K13092: Overview of securing access to the BIG-IP system
o K46122561: Restricting access to the BIG-IP management interface using
network firewall rules
o K92748202: Restricting access to the BIG-IQ management interface using
network firewall rules
Supplemental Information
o K41942608: Overview of security advisory articles
o K4602: Overview of the F5 security vulnerability response policy
o K4918: Overview of the F5 critical issue hotfix policy
o K8986: F5 software lifecycle policy
o K9502: BIG-IP hotfix and point release matrix
o K13123: Managing BIG-IP product hotfixes (11.x - 16.x)
o K15106: Managing BIG-IQ product hotfixes
o K15113: BIG-IQ hotfix and point release matrix
o K48955220: Installing an OPSWAT Endpoint Security update on BIG-IP APM
systems (11.4.x and later)
o K167: Downloading software and firmware from F5
o K9970: Subscribing to email notifications regarding F5 products
o K9957: Creating a custom RSS feed to view new and updated documents
o Expat XML parser documentation
Note: The previous link takes you to a resource outside of AskF5. The
third-party could remove the document without our knowledge.
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