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Critical severity · published May 20, 2026
CVE-2026-3593
Heap use-after-free vulnerability in BIND 9 DNS-over-HTTPS implementation
9.8
CVSS
1.5%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.5% · higher than 75% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
B9
BIND 9 · ISC
9.20.0 through 9.20.22; 9.21.0 through 9.21.21; 9.20.9-S1 through 9.20.22-S1 · source: vendor
BI
Bind · Isc
9.20.0 before 9.20.23; 9.21.0 before 9.21.22 · source: NVD
RH
Red Hat Hardened Images · Red Hat
All versions, or not specified · source: CISA
Affected product
B9
BIND 9
ISC
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3593
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-3593
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-2026-3593
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:7412
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-3593
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2479770
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