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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2021.4107 K50839343: NGINX ModSecurity WAF vulnerability CVE-2021-42717 6 December 2021 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: NGINX ModSecurity WAF Publisher: F5 Networks Operating System: Network Appliance Impact/Access: Denial of Service -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2021-427171 Original Bulletin: https://support.f5.com/csp/article/K50839343 - --------------------------BEGIN INCLUDED TEXT-------------------- K50839343: NGINX ModSecurity WAF vulnerability CVE-2021-42717 Original Publication Date: 04 Dec, 2021 Security Advisory Description ** RESERVED ** This candidate has been reserved by an organization or individual that will use it when announcing a new security problem. When the candidate has been publicized, the details for this candidate will be provided. (CVE-2021-42717) Impact An attacker using specifically formatted JSON messages can cause high resource utilization and potentially denial-of-service (DoS). Security Advisory Status F5 Product Development has assigned ID NWA-1216 (NGINX ModSecurity WAF) to this vulnerability. This issue has been classified as CWE-674: Uncontrolled Recursion (4.6). 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 be |introduced |Severity |score^|component or | | | |vulnerable^1 |in | |2 |feature | +------------+------+-------------+-----------+----------+------+-------------+ |NGINX |R19 - |R25 |R25+1.0.2-3| | |ModSecurity | |ModSecurity |R25 |R24 |R24+1.0.2-2|Medium |5.3 |JSON parser | |WAF | | | | | | | +------------+------+-------------+-----------+----------+------+-------------+ |NGINX Plus |R19 - |None |Not |Not |None |None | | |R25 | |applicable |vulnerable| | | +------------+------+-------------+-----------+----------+------+-------------+ | |16.x |None |Not | | | | | | | |applicable | | | | | +------+-------------+-----------+ | | | | |15.x |None |Not | | | | | | | |applicable | | | | | +------+-------------+-----------+ | | | | |14.x |None |Not | | | | |BIG-IP (all | | |applicable |Not | | | |modules) +------+-------------+-----------+vulnerable|None |None | | |13.x |None |Not | | | | | | | |applicable | | | | | +------+-------------+-----------+ | | | | |12.x |None |Not | | | | | | | |applicable | | | | | +------+-------------+-----------+ | | | | |11.x |None |Not | | | | | | | |applicable | | | | +------------+------+-------------+-----------+----------+------+-------------+ | |8.x |None |Not | | | | | | | |applicable | | | | |BIG-IQ +------+-------------+-----------+ | | | |Centralized |7.x |None |Not |Not |None |None | |Management | | |applicable |vulnerable| | | | +------+-------------+-----------+ | | | | |6.x |None |Not | | | | | | | |applicable | | | | +------------+------+-------------+-----------+----------+------+-------------+ |F5OS |1.x |None |Not |Not |None |None | | | | |applicable |vulnerable| | | +------------+------+-------------+-----------+----------+------+-------------+ |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. 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 To mitigate this vulnerability, you can either upgrade to a fixed version or disable JSON request body processing by disabling any ModSecurity rules that activate the JSON parser. Use your system package manager to view the current dynamic module version or to update to the most recent module version from the NGINX module repository. For more information, refer to Installing the NGINX ModSecurity WAF. Impact of action: When JSON parsing rules are disabled, the system does not parse HTTP request bodies that are in JSON format. Typically that is HTTP requests with the Content-Type header application/json. Before modifying the configuration, you should perform changes in a test environment to ensure compatibility. You should implement modifications to your production environment during a maintenance window to allow for time to revert changes if necessary. Supplemental Information o Trustwave SpiderLabs ModSecurity DoS Vulnerability in JSON parsing (CVE-2021-427171) Note: The previous link take you to a resource outside of AskF5. The third-party could remove the document without our knowledge. 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 K9970: Subscribing to email notifications regarding F5 products o K9957: Creating a custom RSS feed to view new and updated documents - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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