ISC BIND up to 9.21.25 Zone Transfer improper authentication

Summaryinfo

A vulnerability classified as very critical was found in ISC BIND up to 9.18.50/9.18.50-S1/9.20.27/9.20.27-S1/9.21.25. This vulnerability affects unknown code of the component Zone Transfer. Executing a manipulation can lead to improper authentication. This vulnerability appears as CVE-2026-19033. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability has been found in ISC BIND up to 9.18.50/9.18.50-S1/9.20.27/9.20.27-S1/9.21.25 and classified as very critical. This vulnerability affects an unknown function of the component Zone Transfer. The manipulation with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

For a secondary zone with transfers restricted by TSIG, `named` may start to serve the data provided in a zone transfer before the final message with the TSIG signature arrives. This could allow an attacker that does not actually possess a valid TSIG signature to send unauthorized zone contents to a secondary server. Although no TSIG signature ever arrives, `named` does not rollback to the pre-transfer state. To exploit the vulnerability, the transfer must be a multi-message TCP IXFR, as described by RFC 8945. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

The advisory is available at kb.isc.org. This vulnerability was named CVE-2026-19033 since 08/06/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 09/16/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Domain Name Software

Vendor

• ISC

Name

• BIND

Version

• 9.18.0
• 9.18.1
• 9.18.2
• 9.18.3
• 9.18.4
• 9.18.5
• 9.18.6
• 9.18.7
• 9.18.8
• 9.18.9
• 9.18.10
• 9.18.11
• 9.18.12
• 9.18.13
• 9.18.14
• 9.18.15
• 9.18.16
• 9.18.17
• 9.18.18
• 9.18.19
• 9.18.20
• 9.18.21
• 9.18.22
• 9.18.23
• 9.18.24
• 9.18.25
• 9.18.26
• 9.18.27
• 9.18.28
• 9.18.29
• 9.18.30
• 9.18.31
• 9.18.32
• 9.18.33
• 9.18.34
• 9.18.35
• 9.18.36
• 9.18.37
• 9.18.38
• 9.18.39
• 9.18.40
• 9.18.41
• 9.18.42
• 9.18.43
• 9.18.44
• 9.18.45
• 9.18.46
• 9.18.47
• 9.18.48
• 9.18.49
• 9.18.50
• 9.18.50-S1
• 9.20.0
• 9.20.1
• 9.20.2
• 9.20.3
• 9.20.4
• 9.20.5
• 9.20.6
• 9.20.7
• 9.20.8
• 9.20.9
• 9.20.10
• 9.20.11
• 9.20.12
• 9.20.13
• 9.20.14
• 9.20.15
• 9.20.16
• 9.20.17
• 9.20.18
• 9.20.19
• 9.20.20
• 9.20.21
• 9.20.22
• 9.20.23
• 9.20.24
• 9.20.25
• 9.20.26
• 9.20.27
• 9.20.27-S1
• 9.21.0
• 9.21.1
• 9.21.2
• 9.21.3
• 9.21.4
• 9.21.5
• 9.21.6
• 9.21.7
• 9.21.8
• 9.21.9
• 9.21.10
• 9.21.11
• 9.21.12
• 9.21.13
• 9.21.14
• 9.21.15
• 9.21.16
• 9.21.17
• 9.21.18
• 9.21.19
• 9.21.20
• 9.21.21
• 9.21.22
• 9.21.23
• 9.21.24
• 9.21.25

License

• open-source

Website

• Vendor: https://www.isc.org/

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