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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2022.1150 CVE-2021-25220: DNS forwarders - cache poisoning vulnerability 17 March 2022 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Bind Publisher: ISC Operating System: UNIX variants (UNIX, Linux, OSX) Windows Resolution: Patch/Upgrade CVE Names: CVE-2021-25220 Original Bulletin: https://kb.isc.org/docs/cve-2021-25220 Comment: CVSS (Max): 6.2 CVE-2021-25220 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N) CVSS Source: ISC Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N - --------------------------BEGIN INCLUDED TEXT-------------------- CVE: CVE-2021-25220 Document version: 2.0 Posting date: 16 March 2022 Program impacted: BIND Versions affected: BIND 9.11.0 -> 9.11.36 9.12.0 -> 9.16.26 9.17.0 -> 9.18.0 BIND Supported Preview Editions: 9.11.4-S1 -> 9.11.36-S1 9.16.8-S1 -> 9.16.26-S1 Versions of BIND 9 earlier than those shown - back to 9.1.0, including Supported Preview Editions - are also believed to be affected but have not been tested as they are EOL. Severity: Medium Exploitable: Remotely Description: When using forwarders, bogus NS records supplied by, or via, those forwarders may be cached and used by named if it needs to recurse for any reason, causing it to obtain and pass on potentially incorrect answers. Some examples of configurations that will be vulnerable are: * Resolvers using per zone or global forwarding with `forward first` (`forward first` is the default). * Resolvers not using global forwarding, but with per-zone forwarding with either `forward first` (the default) or `forward only`. * Resolvers configured with global forwarding along with zone statements that disable forwarding for part of the DNS namespace. Authoritative-only BIND 9 servers are not vulnerable to this flaw. Impact: The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients. CVSS Score: 6.2 CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N/E:U/RL:U/RC:C For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N/E:U/RL:U/RC:C&version=3.1 Workarounds: If applicable, modify your configuration to either remove all forwarding or all possibility of recursion. Depending on your use-case, it may be possible to use other zone types to replace forward zones. Active exploits: We are not aware of any active exploits. Solution: Upgrade to the patched release most closely related to your current version of BIND: BIND 9.11.37 BIND 9.16.27 BIND 9.18.1 BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers. BIND 9.11.37-S1 BIND 9.16.27-S1 Acknowledgments: ISC would like to thank Xiang Li, Baojun Liu, and Chaoyi Lu from Network and Information Security Lab, Tsinghua University and Changgen Zou from Qi An Xin Group Corp. for discovering and reporting this issue. Document revision history: 1.0 Early Notification, 9 March 2022 1.1 Correction to official document link, 16 March 2022 2.0 Public disclosure, 16 March 2022 Related documents: See our BIND 9 Security Vulnerability Matrix for a complete listing of security vulnerabilities and versions affected: https://kb.isc.org/docs/aa-00913 Do you still have questions? Questions regarding this advisory should go to security-officer@isc.org. To report a new issue, please encrypt your message using security-officer@isc.org's PGP key which can be found here: https://www.isc.org/pgpkey/. If you are unable to use encrypted email, you may also report new issues at: https://www.isc.org/reportbug/. Note: ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see https://www.isc.org/download/.) ISC Security Vulnerability Disclosure Policy: Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy at https://kb.isc.org/docs/aa-00861 The Knowledgebase article https://kb.isc.org/docs/cve-2021-25220 is the complete and official security advisory document. Legal Disclaimer: Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time. A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors. - --------------------------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. 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