CVE-2026-5947

7.5 HIGH

Undefined behavior may result due to a race condition leading to a use-after-free violation

Published: 2026-05-20 · Last updated: 2026-05-21

Severity and scoring

CVSS: 7.5 HIGH
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-362, CWE-416

Affected products

Vendor	Product
isc	bind

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.

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-5947
[Patch]https://downloads.isc.org/isc/bind9/9.20.23
[Patch]https://downloads.isc.org/isc/bind9/9.21.22
[Vendor advisory]https://kb.isc.org/docs/cve-2026-5947

Related CVEs

Same vendor

CVE-2026-5950 — An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthen... (5.3 MEDIUM)
CVE-2026-5946 — Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, ... (7.5 HIGH)
CVE-2026-3593 — A use-after-free vulnerability exists within the DNS-over-HTTPS implementation (7.4 HIGH)
CVE-2026-3592 — BIND resolvers are vulnerable to an amplified resource consumption/exhaustion attack (5.3 MEDIUM)
CVE-2026-3039 — BIND servers that are configured to use TKEY-based authentication via GSS-API tokens are vulnerable to excessive memory consumption when ... (7.5 HIGH)

Same CWE

CVE-2026-45782 — Cloud Hypervisor is a Virtual Machine Monitor for Cloud workloads
CVE-2026-47955 — Acrobat Reader versions 24.001.30365, 26.001.21651 and earlier are affected by a Use After Free vulnerability that could result in arbitr... (7.8 HIGH)
CVE-2026-47924 — Acrobat Reader versions 24.001.30365, 26.001.21651 and earlier are affected by a Use After Free vulnerability that could lead to disclosu... (5.5 MEDIUM)
CVE-2026-47921 — Acrobat Reader versions 24.001.30365, 26.001.21651 and earlier are affected by a Use After Free vulnerability that could result in arbitr... (7.8 HIGH)
CVE-2026-47920 — Acrobat Reader versions 24.001.30365, 26.001.21651 and earlier are affected by a Use After Free vulnerability that could result in arbitr... (7.8 HIGH)