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ISC BIND 9.20.0 < 9.20.23 / 9.20.9-S1 < 9.20.23-S1 / 9.21.0 < 9.21.22 Vulnerability (cve-2026-5947)

medium Nessus Plugin ID 315662

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Synopsis

The remote name server is affected by a vulnerability vulnerability.

Description

The version of ISC BIND installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the cve-2026-5947 advisory.

 - Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the recursive-clients limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected. (CVE-2026-5947)

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 9.20.23 / 9.20.23-S1 / 9.21.22 or later.

See Also

https://kb.isc.org/v1/docs/cve-2026-5947

Plugin Details

Severity: Medium

ID: 315662

File Name: bind9_92122_cve-2026-5947.nasl

Version: 1.4

Type: Remote

Family: DNS

Published: 5/20/2026

Updated: 5/26/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4

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

CVSS Score Source: CVE-2026-5947

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:isc:bind

Required KB Items: Settings/ParanoidReport, bind/version

Exploit Ease: No known exploits are available

Patch Publication Date: 5/20/2026

Vulnerability Publication Date: 5/20/2026

Reference Information

CVE: CVE-2026-5947

IAVA: 2026-A-0498