CVE-2026-5947

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://downloads.isc.org/isc/bind9/9.20.23	Patch
https://downloads.isc.org/isc/bind9/9.21.22	Patch
https://kb.isc.org/docs/cve-2026-5947	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:isc:bind:::::-:::*
	cpe:2.3:a:isc:bind:::::-:::*

History

21 May 2026, 15:24

Type	Values Removed	Values Added
References	~~() https://downloads.isc.org/isc/bind9/9.20.23 -~~	() https://downloads.isc.org/isc/bind9/9.20.23 - Patch
References	~~() https://downloads.isc.org/isc/bind9/9.21.22 -~~	() https://downloads.isc.org/isc/bind9/9.21.22 - Patch
References	~~() https://kb.isc.org/docs/cve-2026-5947 -~~	() https://kb.isc.org/docs/cve-2026-5947 - Vendor Advisory
First Time		Isc bind Isc
CPE		cpe:2.3:a:isc:bind:::::-:::*

20 May 2026, 13:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-20 13:16

Updated : 2026-05-21 15:24

NVD link : CVE-2026-5947

Mitre link : CVE-2026-5947

CVE.ORG link : CVE-2026-5947

JSON object : View

Products Affected

isc

bind

CWE

CWE-362

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

CWE-416

Use After Free

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