CVE-2026-5947 (GCVE-0-2026-5947)

Vulnerability from cvelistv5 – Published: 2026-05-20 13:10 – Updated: 2026-05-20 13:39
VLAI
Title
SIG(0) validation during query flood may lead to undefined behavior
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
  • CWE-416 - Use After Free
Assigner
isc
References
Impacted products
Vendor Product Version
ISC BIND 9 Affected: 9.20.0 , ≤ 9.20.22 (custom)
Affected: 9.21.0 , ≤ 9.21.21 (custom)
Affected: 9.20.9-S1 , ≤ 9.20.22-S1 (custom)
Unaffected: 9.18.28 , ≤ 9.18.49 (custom)
Unaffected: 9.18.28-S1 , ≤ 9.18.49-S1 (custom)
Create a notification for this product.
Date Public
2026-05-20 00:00
Credits
ISC would like to thank Naoki Wakamatsu for bringing this vulnerability to our attention.
Show details on NVD website
To clipboard 

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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