{"document":{"acknowledgments":[{"urls":["https://kb.cert.org/vuls/id/589825#acknowledgements"]}],"category":"CERT/CC Vulnerability Note","csaf_version":"2.0","notes":[{"category":"summary","text":"### Overview\r\nDevices supporting both Bluetooth BR/EDR and LE using Cross-Transport Key Derivation (CTKD) for pairing are vulnerable to key overwrite, which enables an attacker to to gain additional access to profiles or services that are not restricted by reducing the encryption key strength or overwriting an authenticated key with an unauthenticated key. This vulnerability is being referred to as [BLURtooth](https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/blurtooth/).\r\n\r\n### Description\r\nAs detailed in both the Bluetooth Core Specification versions [4.2](https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=441541) and [5.0](https://www.bluetooth.org/docman/handlers/DownloadDoc.ashx?doc_id=421043), Bluetooth CTKD can be used for pairing by devices that support both Low Energy (BLE) and Basic Rate/Enhanced Data Rate (BR/EDR) transport methods, which are known as \"dual-mode\" devices. CTKD pairing allows the devices to pair once using either transport method while generating both the BR/EDR and LE Long Term Keys (LTK) without needing to pair a second time. Dual-mode devices using CTKD to generate a LTK or Link Key (LK) are able to overwrite the original LTK or LK in cases where that transport was enforcing a higher level of security.\r\n\r\n### Impact\r\nSeveral potential attacks could be performed by exploiting [CVE-2020-15802](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15802), including a Man in the Middle (MITM) attack. The vulnerability is being referred to as BLURtooth and the group of attacks is being referred to as the BLUR attacks. Vulnerable devices must permit a pairing or bonding to proceed transparently with no authentication, or a weak key strength, on at least one of the BR/EDR or LE transports in order to be susceptible to attack. For example, it may be possible to pair with certain devices using [JustWorks](https://www.bluetooth.com/blog/bluetooth-pairing-part-4/) pairing over BR/EDR or LE and overwriting an existing LTK or LK on the other transport. When this results in the reduction of encryption key strength or the overwrite of an authenticated key with an unauthenticated key, an attacker could gain additional access to profiles or services that are not otherwise restricted.\r\n\r\n### Solution\r\nThe Bluetooth SIG has released [recommendations](https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/blurtooth/) for mitigating this issue that include additional conformance tests to ensure that the overwrite of an authenticated key or a key of a given length with an unauthenticated key or a key of reduced length is not permitted in devices supporting Bluetooth Core Specification version 5.1 or greater. They also recommend that potentially vulnerable implementations introduce the restrictions on CTKD mandated in Bluetooth Core Specification versions 5.1 and later. Implementations should disallow overwrite of the LTK or LK for one transport with the LTK or LK derived from the other when this overwrite would result in either a reduction of the key strength of the original bonding or a reduction in the MITM protection of the original bonding (from authenticated to unauthenticated). This may require that the host track the negotiated length and authentication status of the keys in the Bluetooth security database.\r\n\r\nThe Bluetooth SIG further recommends that devices restrict when they are pairable on either transport to times when user interaction places the device into a pairable mode or when the device has no bonds or existing connections to a paired device. In all cases, it is recommended that devices restrict the duration of pairing mode and overwrite an existing bonding only when devices are explicitly in pairing mode.\r\n\r\n### Acknowledgements\r\nThanks to the reporter who wishes to remain anonymous.\r\n\r\n This document was written by Madison Oliver.","title":"Summary"},{"category":"legal_disclaimer","text":"THIS DOCUMENT IS PROVIDED ON AN 'AS IS' BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. ","title":"Legal Disclaimer"},{"category":"other","text":"CERT/CC Vulnerability Note is a limited advisory. It primarily identifies vendors impacted by the advisory and not specific products. We only support \"known_affected\" and \"known_not_affected\" status. Please consult the vendor's statements and advisory URL if provided by the vendor for more details ","title":"Limitations of Advisory"},{"category":"other","text":"Based on our investigation we confirm that there are no platforms/products which are affected from these vulnerabilities.","title":"Vendor statment from Juniper Networks"},{"category":"other","text":"Arista products do not use bluetooth and are hence not affected.","title":"Vendor statment from Arista Networks Inc."},{"category":"other","text":"No Brocade Fibre Channel Products from Broadcom are currently known to be affected by this vulnerability.","title":"Vendor statment from Brocade Communication Systems"},{"category":"other","text":"Belden devices do not support Bluetooth and are not affected by this vulnerability.","title":"Vendor statment from Belden"},{"category":"other","text":"F5 products do not include/support Bluetooth.","title":"Vendor statment from F5 Networks Inc."},{"category":"other","text":"Microchip Bluetooth Dual Mode solutions do NOT implement Cross-Transport Key Derivation (CTKD), Microchip solutions are NOT affected by BLURtooth vulnerability","title":"Vendor statment from Microchip Technology"},{"category":"other","text":"Zyxel products are NOT affected either because they don’t support Cross Transport Key Derivation or do not support Bluetooth at all.","title":"Vendor statment from Zyxel"},{"category":"other","text":"Vmware is not affected by the above issues directly.","title":"Vendor statment from VMware"}],"publisher":{"category":"coordinator","contact_details":"Email: cert@cert.org, Phone: +1412 268 5800","issuing_authority":"CERT/CC under DHS/CISA https://www.cisa.gov/cybersecurity also see https://kb.cert.org/ ","name":"CERT/CC","namespace":"https://kb.cert.org/"},"references":[{"url":"https://certcc.github.io/certcc_disclosure_policy","summary":"CERT/CC vulnerability disclosure policy"},{"summary":"CERT/CC document released","category":"self","url":"https://kb.cert.org/vuls/id/589825"},{"url":"https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/blurtooth/","summary":"https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/blurtooth/"},{"url":"https://www.bluetooth.com/specifications/bluetooth-core-specification/","summary":"https://www.bluetooth.com/specifications/bluetooth-core-specification/"},{"url":"https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/reporting-security/","summary":"https://www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/bluetooth-security/reporting-security/"},{"url":"https://support2.windriver.com/index.php?page=cve&on=view&id=CVE-2020-15802","summary":"Reference(s) from vendor \"Wind River\""}],"title":"Devices supporting Bluetooth BR/EDR and LE using CTKD are vulnerable to key overwrite","tracking":{"current_release_date":"2021-02-16T16:47:27+00:00","generator":{"engine":{"name":"VINCE","version":"3.0.35"}},"id":"VU#589825","initial_release_date":"2020-09-09 16:58:49.231003+00:00","revision_history":[{"date":"2021-02-16T16:47:27+00:00","number":"1.20210216164727.10","summary":"Released on 2021-02-16T16:47:27+00:00"}],"status":"final","version":"1.20210216164727.10"}},"vulnerabilities":[{"title":"Devices supporting both Bluetooth BR/EDR and BLE using Cross-Transport Key Derivation for pairing are vulnerable to key overwrite.","notes":[{"category":"summary","text":"Devices supporting both Bluetooth BR/EDR and BLE using Cross-Transport Key Derivation for pairing are vulnerable to key overwrite. This could cause the reduction of encryption key strength or overwrite of an authenticated key with an unauthenticated key. This may allow an attacker to gain additional access to profiles or services that are not restricted. This vulnerability is being referred to as BLURtooth."}],"cve":"CVE-2020-15802","ids":[{"system_name":"CERT/CC V Identifier ","text":"VU#589825"}],"product_status":{"known_affected":["CSAFPID-f3032724-3a7c-11f1-a172-0afffb3ee71d"],"known_not_affected":["CSAFPID-f2fe3c1e-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2fe7cce-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2fec38c-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2ff2fa2-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2ff7264-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2ffb4d6-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f2ffefdc-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f3003a46-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f3006ce6-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f300acba-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f300fd5a-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f3013766-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f30177d0-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f301c636-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f301feb2-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f3025b0a-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f302b0be-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f302e4c6-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f3036b94-3a7c-11f1-a172-0afffb3ee71d","CSAFPID-f303a794-3a7c-11f1-a172-0afffb3ee71d"]}}],"product_tree":{"branches":[{"category":"vendor","name":"Fujitsu","product":{"name":"Fujitsu Products","product_id":"CSAFPID-f2fe3c1e-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Arista Networks Inc.","product":{"name":"Arista Networks Inc. Products","product_id":"CSAFPID-f2fe7cce-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Palo Alto Networks","product":{"name":"Palo Alto Networks Products","product_id":"CSAFPID-f2fec38c-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"NetBSD","product":{"name":"NetBSD Products","product_id":"CSAFPID-f2ff2fa2-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"lwIP","product":{"name":"lwIP Products","product_id":"CSAFPID-f2ff7264-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Fastly","product":{"name":"Fastly Products","product_id":"CSAFPID-f2ffb4d6-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Brocade Communication Systems","product":{"name":"Brocade Communication Systems Products","product_id":"CSAFPID-f2ffefdc-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Barracuda Networks","product":{"name":"Barracuda Networks Products","product_id":"CSAFPID-f3003a46-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Wind River","product":{"name":"Wind River Products","product_id":"CSAFPID-f3006ce6-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Ceragon Networks Inc","product":{"name":"Ceragon Networks Inc Products","product_id":"CSAFPID-f300acba-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Belden","product":{"name":"Belden Products","product_id":"CSAFPID-f300fd5a-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"F5 Networks Inc.","product":{"name":"F5 Networks Inc. Products","product_id":"CSAFPID-f3013766-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Intel","product":{"name":"Intel Products","product_id":"CSAFPID-f30177d0-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Juniper Networks","product":{"name":"Juniper Networks Products","product_id":"CSAFPID-f301c636-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Infoblox","product":{"name":"Infoblox Products","product_id":"CSAFPID-f301feb2-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Microchip Technology","product":{"name":"Microchip Technology Products","product_id":"CSAFPID-f3025b0a-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Miredo","product":{"name":"Miredo Products","product_id":"CSAFPID-f302b0be-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Zyxel","product":{"name":"Zyxel Products","product_id":"CSAFPID-f302e4c6-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"Bluetooth SIG","product":{"name":"Bluetooth SIG Products","product_id":"CSAFPID-f3032724-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"VMware","product":{"name":"VMware Products","product_id":"CSAFPID-f3036b94-3a7c-11f1-a172-0afffb3ee71d"}},{"category":"vendor","name":"VMware Carbon Black","product":{"name":"VMware Carbon Black Products","product_id":"CSAFPID-f303a794-3a7c-11f1-a172-0afffb3ee71d"}}]}}