CVE-2026-5947

Severity CVSS v4.0:

Pending analysis

Type:

CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Publication date:

20/05/2026

Last modified:

21/05/2026

Description

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.<br /> 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.<br /> BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS v3.1 Severity and Metrics:

Base Score: 7.50 HIGH
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): High

Base Score 3.x

7.50

Severity 3.x

HIGH

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:a:isc:bind:::::-:::*	9.20.0 (including)	9.20.23 (excluding)
cpe:2.3:a:isc:bind:::::-:::*	9.21.0 (including)	9.21.22 (excluding)

To consult the complete list of CPE names with products and versions, see this page

CVE-2026-5947

Description

Impact

Vulnerable products and versions

References to Advisories, Solutions, and Tools