PT-2026-42164 · Isc · Bind 9

Published 2026-05-17 · Updated 2026-05-21 · CVE-2026-5947

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions BIND 9 versions 9.20.0 through 9.20.22 BIND 9 versions 9.21.0 through 9.21.21 BIND 9 versions 9.20.9-S1 through 9.20.22-S1

Description A race condition occurs when BIND receives an incoming DNS message signed with SIG(0). While validating the signature, if the recursive-clients limit is reached (such as during a query flood) and the message is discarded, a use-after-free violation may occur. This happens because the SIG(0) validation process may attempt to read the DNS message after it has been discarded, leading to undefined behavior. Use-after-free is a scenario where a program continues to use a pointer after it has been freed, which can lead to crashes or unpredictable execution.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Race Condition

Use After Free

Weakness Enumeration

CWE-362

CWE-416

Related Identifiers

CVE-2026-5947

USN-8293-1

Affected Products

Bind 9

References · 17

• https://ubuntu.com/security/CVE-2026-5947 · Vendor Advisory
• https://downloads.isc.org/isc/bind9/9.20.23 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-5947 · Security Note
• https://ubuntu.com/security/CVE-2026-3593 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-3039 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-5947 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-5946 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-5947 · Security Note
• https://ubuntu.com/security/notices/USN-8293-1 · Vendor Advisory
• https://kb.isc.org/docs/cve-2026-5947 · Vendor Advisory
• https://osv.dev/vulnerability/USN-8293-1 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-3592 · Vendor Advisory
• https://downloads.isc.org/isc/bind9/9.21.22 · Patch
• https://ubuntu.com/security/CVE-2026-5950 · Vendor Advisory
• https://reddit.com/r/dns/comments/1tfzbla/preannouncement_of_bind_9_security_issues · Reddit Post