CVE-2026-5947 Details
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. 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.
A race condition in ISC 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 can cause undefined behavior due to a use-after-free violation. When BIND receives a DNS message signed with SIG(0), it validates the signature. If the 'recursive-clients' limit is reached during this process, the message may be discarded. This creates a brief window where the validation can attempt to read the discarded message, leading to potential memory corruption.
Users can upgrade to BIND 9.20.23, 9.21.22, or 9.20.23-S1 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 20, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-362 | Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') | [email protected] |
| CWE-367 | Time-of-check Time-of-use (TOCTOU) Race Condition | redhat-SADP |
| CWE-416 | Use After Free | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| isc bind | >= 9.20.0, < 9.20.23 >= 9.21.0, < 9.21.22 |
CPE
Remediation
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Change History
8 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 24, 2026 | CVE Modified | redhat-SADP |
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jul 15, 2026 | CVE Modified | redhat-SADP |
| Jun 30, 2026 | CVE Modified | redhat-SADP |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 21, 2026 | Initial Analysis | [email protected] |
| May 20, 2026 | New CVE Received | [email protected] |