A vulnerability was found in ISC BIND up to 9.15.4 (Domain Name Software) and classified as problematic. This issue affects an unknown functionality of the component Mirror Zone Handler. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is integrity. The summary by CVE is:

Mirror zones are a BIND feature allowing recursive servers to pre-cache zone data provided by other servers. A mirror zone is similar to a zone of type secondary, except that its data is subject to DNSSEC validation before being used in answers, as if it had been looked up via traditional recursion, and when mirror zone data cannot be validated, BIND falls back to using traditional recursion instead of the mirror zone. However, an error in the validity checks for the incoming zone data can allow an on-path attacker to replace zone data that was validated with a configured trust anchor with forged data of the attacker's choosing. The mirror zone feature is most often used to serve a local copy of the root zone. If an attacker was able to insert themselves into the network path between a recursive server using a mirror zone and a root name server, this vulnerability could then be used to cause the recursive server to accept a copy of falsified root zone data. This affects BIND versions 9.14.0 up to 9.14.6, and 9.15.0 up to 9.15.4.

The weakness was shared 10/17/2019 (Website). It is possible to read the advisory at kb.isc.org. The identification of this vulnerability is CVE-2019-6475 since 01/16/2019. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The advisory points out:

Mirror zones are a BIND feature allowing recursive servers to pre-cache zone data provided by other servers. A mirror zone is similar to a zone of type secondary, except that its data is subject to DNSSEC validation before being used in answers, as if it had been looked up via traditional recursion, and when mirror zone data cannot be validated, BIND falls back to using traditional recursion instead of the mirror zone. However, an error in the validity checks for the incoming zone data can allow an on-path attacker to replace zone data that was validated with a configured trust anchor with forged data of the attacker's choosing.

The advisory illustrates:

An on-path attacker who manages to successfully exploit this vulnerability can replace the mirrored zone (usually the root) with data of their own choosing, effectively bypassing DNSSEC protection.

Upgrading to version 9.14.7 or 9.15.5 eliminates this vulnerability. It is possible to mitigate the problem by applying the configuration setting Disable Mirror Zones. The best possible mitigation is suggested to be upgrading to the latest version.

The entry 143880 is related to this item.

Productinfo

Type

• Domain Name Software

Vendor

• ISC

Name

• BIND

Version

• 9.14.0
• 9.14.1
• 9.14.2
• 9.14.3
• 9.14.4
• 9.14.5
• 9.14.6
• 9.15.0
• 9.15.1
• 9.15.2
• 9.15.3
• 9.15.4

License

• open-source

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• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

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