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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2020.3101.2 BIG-IP SSL/TLS ADH/DHE vulnerability CVE-2020-5929 25 September 2020 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: F5 Products Publisher: F5 Networks Operating System: Network Appliance Impact/Access: Access Privileged Data -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2020-5929 Original Bulletin: https://support.f5.com/csp/article/K91158923 Revision History: September 25 2020: Minor notification update September 10 2020: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- K91158923:BIG-IP SSL/TLS ADH/DHE vulnerability CVE-2020-5929 Security Advisory Original Publication Date: 09 Sep, 2020 Latest Publication Date: 25 Sep, 2020 Security Advisory Description BIG-IP platforms with Cavium Nitrox SSL hardware acceleration cards, a virtual server configured with a Client SSL profile, and using Anonymous Diffie-Hellman (ADH) or Ephemeral Diffie-Hellman (DHE) key exchange and Single DH use option not enabled in the options list may be vulnerable to crafted SSL/Transport Layer Security (TLS) handshakes that may result with a pre-master secret (PMS) that starts in a 0 byte and may lead to a recovery of plaintext messages as BIG-IP TLS/SSL ADH/DHE sends different error messages acting as an oracle. Differences in processing time when the PMS starts with 0 byte coupled with very precise timing measurement observation may also expose this vulnerability. (CVE-2020-5929) Impact Exploiting this vulnerability requires multiple crafted SSL/TLS handshakes to the vulnerable BIG-IP virtual server. This vulnerability may make it possible to recover the shared secret of past sessions and perform plaintext recovery of encrypted messages. Only SSL/TLS sessions established using cipher suites that use ADH or DHE key exchange are vulnerable to this attack. Captured SSL/TLS sessions encrypted with cipher suites using the RSA key exchange are not at risk for subsequent decryption due to this vulnerability. This vulnerability affects BIG-IP systems with virtual servers associated with a Client SSL profile and only if all of the following conditions are met: o You are using ADH or DHE key exchange in the Client SSL profile. Note: DHE is enabled by default in the DEFAULT cipher suite. ADH is not available in the DEFAULT cipher suite. o You have not enabled the Single Diffie-Hellman use option-or Single DH use option-in the Client SSL profile. Note: The Single DH use option is not enabled by default in the Client SSL profile options list. o Your BIG-IP platform has a Cavium Nitrox SSL hardware acceleration card installed. Platforms with this installed include: BIG-IP i11400-DS, i11600-DS, i11800-DS BIG-IP 1600, 3600, 3900, 5000, 6900, 7000, 8900, 10000, 11000, 12000 VIPRION 2100, 2150, 2250, 4100, 4200, 4300 Security Advisory Status F5 Product Development has assigned ID 693211 (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 or | | | |be |in | |1 |feature | | | |vulnerable| | | | | +---------------+------+----------+----------+----------+------+--------------+ | |16.x |None |Not | | | | | | | |applicable| | | | | +------+----------+----------+ | | | |BIG-IP (LTM, |15.x |None |Not | | | | |AAM, Advanced | | |applicable| | |Client SSL | |WAF, AFM, +------+----------+----------+ | |profile with | |Analytics, APM,|14.x |None |14.0.0 | | |ADH or DHE key| |ASM, DDHD, DNS,+------+----------+----------+High |7.4 |exchange | |FPS, GTM, Link |13.x |13.0.0 |13.1.0 | | |enabled and | |Controller, | | |13.0.0 HF3| | |Single DH use | |PEM, SSLO) +------+----------+----------+ | |option | | |12.x |12.1.0 - |12.1.3 | | |disabled | | | |12.1.2 HF1|12.1.2 HF2| | | | | +------+----------+----------+ | | | | |11.x |11.6.1 - |11.6.3 | | | | | | |11.6.2 |11.6.2 HF1| | | | +---------------+------+----------+----------+----------+------+--------------+ | |7.x |None |Not | | | | | | | |applicable| | | | |BIG-IQ +------+----------+----------+ | | | |Centralized |6.x |None |Not |Not |None |None | |Management | | |applicable|vulnerable| | | | +------+----------+----------+ | | | | |5.x |None |Not | | | | | | | |applicable| | | | +---------------+------+----------+----------+----------+------+--------------+ |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 You can mitigate this issue by enabling Single DH use, disabling ADH and DHE ciphers, and enabling Unclean Shutdown in the Client SSL profile. Note: DHE key exchange is available in the DEFAULT cipher string. ADH key exchange is not available in the DEFAULT cipher string. To do so, perform the following procedure: 1. Log in to the Configuration utility. 2. Go to Local Traffic > Profiles > SSL > Client. 3. Select the Client SSL profile. 4. For Configuration, select Advanced. 5. In the Options section, in the list, select Options List. 6. In the Options List section, under Available Options, select Single DH use, and then select Enable. The Single DH Use option displays under Enabled Options. 7. For Ciphers, in the text box, enter a cipher string that disables ADH or DHE, such as the following example: !DHE:!ADH:ALL 8. For Unclean Shutdown, select Enabled. 9. Select Update. Acknowledgements F5 would like to acknowledge Robert Merget and Marcus Brinkmann of Ruhr-University Bochum, Juraj Somorovsky of Paderborn University, and Nimrod Aviram of Tel Aviv University for bringing this issue to our attention and for following the highest standards of coordinated disclosure. 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 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 - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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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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