Is CVE-2026-3593 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-3593 being exploited in the wild.

How severe is CVE-2026-3593?

High severity, with a CVSS score of 7.4, published 20 May 2026.

Which products and versions are affected?

Isc BIND 9 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.20.9-S1 through 9.20.22-S1.

Is there a fix for CVE-2026-3593?

A patch was published on 2026-05-20: Patched versions 9.20.23 and 9.21.22 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-3593 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-3593?

Check whether you run Isc BIND 9 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-3593: ISC BIND 9 use-after-free in DNS-over-HTTPS implementation

CVE-2026-3593 · Severity: high · CVSS 7.4 · Published 2026-05-20

A vulnerability has been identified in BIND 9, the most widely used Domain Name System (DNS) software on the internet. This flaw affects the DNS-over-HTTPS (DoH) feature, which is used to encrypt web-based DNS queries. An attacker could exploit this to cause memory corruption, potentially leading to service crashes or unauthorized access to sensitive information, impacting both authoritative and resolver servers.

Technologies: Isc BIND 9. Vendors: Isc.

Quick answers

Is CVE-2026-3593 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-3593 being exploited in the wild.
How severe is CVE-2026-3593?: High severity, with a CVSS score of 7.4, published 20 May 2026.
Which products and versions are affected?: Isc BIND 9 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.20.9-S1 through 9.20.22-S1.
Is there a fix for CVE-2026-3593?: A patch was published on 2026-05-20: Patched versions 9.20.23 and 9.21.22 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-3593 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-3593?: Check whether you run Isc BIND 9 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A heap use-after-free vulnerability (CWE-416) exists within the DNS-over-HTTPS implementation of BIND 9. The flaw is triggered when a remote attacker sends specially crafted HTTP/2 traffic to a DNS-over-HTTPS endpoint. This can lead to memory corruption, affecting both authoritative servers and resolvers. While the attack is network-reachable and requires no authentication, it has a high attack complexity. Users are advised to upgrade to BIND versions 9.20.23, 9.21.22, or 9.20.23-S1. As a workaround, disabling DNS-over-HTTPS will mitigate the risk.

Affected products

ISC BIND 9 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.20.9-S1 through 9.20.22-S1

Timeline

2026-05-13: other: Early notification provided
2026-05-20: disclosed: Public disclosure of the vulnerability
2026-05-20: patched: Patched versions 9.20.23 and 9.21.22 released

References

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