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AUSCERT External Security Bulletin Redistribution
ESB-2021.1885.2
Python tarfile library vulnerability CVE-2019-20907
14 September 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: BIG-IP (all modules)
BIG-IQ Centralized Management
F5OS
Publisher: F5 Networks
Operating System: Network Appliance
Impact/Access: Denial of Service -- Existing Account
Resolution: Mitigation
CVE Names: CVE-2019-20907
Reference: ESB-2021.0927
ESB-2021.0899
Original Bulletin:
https://support.f5.com/csp/article/K78284681
Revision History: September 14 2021: Vendor updated versions known to be vulnerable
June 2 2021: Initial Release
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K78284681: Python tarfile library vulnerability CVE-2019-20907
Original Publication Date: 02 Jun, 2021
Latest Publication Date: 13 Sep, 2021
Security Advisory Description
In Lib/tarfile.py in Python through 3.8.3, an attacker is able to craft a TAR
archive leading to an infinite loop when opened by tarfile.open, because
_proc_pax lacks header validation. (CVE-2019-20907)
Impact
A user-created custom Python script utilizing the Python tarfile library may
enter an infinite loop, consuming resources and causing a denial of
service. The Python tarfile library is not used by any standard F5-supplied
software.
Security Advisory Status
F5 Product Development has assigned ID 1021245 (BIG-IP), ID 1020793 (BIG-IQ),
and ID 1019165 (F5OS) 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.
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 following table 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 |16.0.0 - |None | | | |
| | |16.0.1 | | | | |
| +------+--------------+----------+ | | |
| |15.x |15.1.0 - |None | | | |
| | |15.1.3 | | | | |
| +------+--------------+----------+ | | |
| |14.x |14.1.0 - |None | | | |
|BIG-IP (all | |14.1.4 | | | |Python |
|modules) +------+--------------+----------+Medium^3 |4.4 |tarfile |
| |13.x |13.1.0 - |None | | |library |
| | |13.1.4 | | | | |
| +------+--------------+----------+ | | |
| |12.x |12.1.0 - |None | | | |
| | |12.1.6 | | | | |
| +------+--------------+----------+ | | |
| |11.x |None |Not | | | |
| | | |applicable| | | |
+------------+------+--------------+----------+----------+------+-------------+
| |8.x |8.0.0 |None | | | |
|BIG-IQ +------+--------------+----------+ | | |
|Centralized |7.x |7.0.0 - 7.1.0 |None |Medium^3 |4.4 |None |
|Management +------+--------------+----------+ | | |
| |6.x |6.0.1 - 6.1.0 |None | | | |
+------------+------+--------------+----------+----------+------+-------------+
|F5OS |1.x |1.1.0 - 1.1.4 |None |Medium^3 |4.4 |None |
+------------+------+--------------+----------+----------+------+-------------+
|Traffix SDC |5.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+------------+------+--------------+----------+----------+------+-------------+
^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.
^3The specified products contain the affected code. However, F5 identifies the
vulnerability status as Not vulnerable because the attacker cannot exploit the
code in default, standard, or recommended configurations.
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
Avoid using custom-written scripts that utilize the Python tarfile libraries on
F5 systems.
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 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
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