Detections
Analytics

ISC BIND 9.18.0 < 9.20.29 / 9.18.11-S1 < 9.20.29-S1 / 9.20.0 < 9.20.29 / 9.20.9-S1 < 9.20.29-S1 / 9.21.0 < 9.21.26 Multiple Vulnerabilities

high Nessus Plugin ID 347971

Synopsis

The remote name server is affected by multiple vulnerabilities.

Description

The version of ISC BIND running on the remote host is 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, or 9.21.0 through 9.21.25. Supported Preview Edition releases 9.18.11-S1 through 9.18.50-S1 and 9.20.9-S1 through 9.20.27-S1 are also affected. It is, therefore, affected by multiple vulnerabilities :

 - A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode records may fail to properly deallocate internal resources. If this happens repeatedly, resource exhaustion will eventually prevent the resolver from performing new recursive lookups. (CVE-2026-81563)

 - If a BIND resolver has cached a tree of SVCB/HTTPS AliasMode records, and is then queried for the root of that tree, the resolver will spend disproportionate CPU time constructing the response. (CVE-2026-81736)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to ISC BIND version 9.20.29 / 9.20.29-S1 / 9.21.26 or later. Note that the 9.18 branch is end of life and no fix is available for it; migrate to a supported branch.

See Also

https://kb.isc.org/docs/aa-00913

https://kb.isc.org/docs/cve-2026-81563

https://kb.isc.org/docs/cve-2026-81736

Plugin Details

Severity: High

ID: 347971

File Name: bind9_92126_cve-2026-81563.nasl

Version: 1.2

Type: Remote

Family: DNS

Published: 9/18/2026

Updated: 9/18/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.7

Percentile: 95.96

CVSS v2

Risk Factor: High

Base Score: 7.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2026-81563

CVSS v3

Risk Factor: High

Base Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vulnerability Information

CPE: cpe:/a:isc:bind

Required KB Items: Settings/ParanoidReport, bind/version

Patch Publication Date: 9/16/2026

Vulnerability Publication Date: 9/16/2026

Reference Information

CVE: CVE-2026-81563, CVE-2026-81736

IAVA: 2026-A-1029