Use-After-Free in BIND 9 DoH (9.20.09.20.22 / 9.21.09.21.21)
CVE-2026-3593 Published on May 20, 2026
Heap use-after-free vulnerability in BIND 9 DNS-over-HTTPS implementation
A use-after-free vulnerability exists within the DNS-over-HTTPS implementation.
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 9.18.0 through 9.18.48 and 9.18.11-S1 through 9.18.48-S1 are NOT affected.
Vulnerability Analysis
CVE-2026-3593 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity, and a high impact on availability.
Weakness Type
What is a Dangling pointer Vulnerability?
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
CVE-2026-3593 has been classified to as a Dangling pointer vulnerability or weakness.
Products Associated with CVE-2026-3593
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Affected Versions
ISC BIND 9:- Version 9.20.0, <= 9.20.22 is affected.
- Version 9.21.0, <= 9.21.21 is affected.
- Version 9.20.9-S1, <= 9.20.22-S1 is affected.
- Version 9.18.0, <= 9.18.48 is unaffected.
- Version 9.18.11-S1, <= 9.18.48-S1 is unaffected.