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Vulnerability · Published May 20, 2026 · Assigned by isc

CVE-2026-3593Heap use-after-free vulnerability in BIND 9 DNS-over-HTTPS implementation

High 7.4

In plain English

A high-severity use-after-free in BIND 9 from ISC. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.5% (higher than 75% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High
Exploit odds (30 days)1.5%top 25.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20bind9.18.49-r0ALPINE-CVE-2026-3593
Alpine:v3.21bind9.18.49-r0ALPINE-CVE-2026-3593
Alpine:v3.22bind9.20.23-r0ALPINE-CVE-2026-3593
Alpine:v3.23bind9.20.23-r0ALPINE-CVE-2026-3593
Alpine:v3.24bind9.20.23-r0ALPINE-CVE-2026-3593
Debian:13bind91:9.20.23-1~deb13u1DEBIAN-CVE-2026-3593
Debian:14bind91:9.20.23-1DEBIAN-CVE-2026-3593
Ubuntu:25.10bind91:9.20.11-1ubuntu2.4UBUNTU-CVE-2026-3593
Ubuntu:26.04:LTSbind91:9.20.18-1ubuntu2.1UBUNTU-CVE-2026-3593

Affected products (as reported)

VendorProductVersions
ISC BIND 9 9.20.0 – through 9.20.229.21.0 – through 9.21.219.20.9-S1 – through 9.20.22-S1

Weakness: CWE-416, CWE-825 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H

References