# CVE-2026-19662: ISC BIND named resolver use-after-free denial of service

Source: https://junglewise.ai/threats/cve-2026-19662-isc-bind-named-resolver-use-after-free-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-19662 · Severity: medium · CVSS 5.9 · Published 2026-09-16

BIND is a widely-used DNS resolver software that handles domain name lookups for organizations and ISPs. A flaw in how BIND processes DNSSEC-signed responses can cause the resolver process to crash when an attacker controls an authoritative nameserver and sends carefully timed, malformed responses. This creates a denial-of-service condition, disrupting DNS resolution for all users depending on that resolver.

Technologies: [Isc Bind](https://junglewise.ai/threats/technologies/bind). Vendors: [Isc](https://junglewise.ai/threats/vendors/isc).

## Quick answers

**Is CVE-2026-19662 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19662 being exploited in the wild.

**How severe is CVE-2026-19662?** Medium severity, with a CVSS score of 5.9, published 16 September 2026.

**Which products and versions are affected?** Isc Bind 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.27-S1.

**Is there a fix for CVE-2026-19662?** A patch was published on 2026-09-16: Fixed in BIND 9.20.29 and 9.20.29-S1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-19662 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-19662?** Check whether you run Isc Bind 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

The vulnerability is a use-after-free bug in BIND's qpcache (query/proof cache) module when processing NOQNAME proofs for DNSSEC-signed zones. An attacker must control an authoritative nameserver and induce a victim resolver to send multiple queries for a DNSSEC-signed zone. By responding with a crafted sequence of answers that arrive in a specific order and timing, the resolver's cache logic dereferences memory that has already been freed, triggering a crash. The attack is remotely exploitable but requires high complexity conditions (AC:H) including precise timing and the attacker's control of an authoritative server. Patches are available in BIND 9.20.29 and 9.20.29-S1.

## Affected products

- ISC BIND 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.27-S1

## Timeline

- 2026-09-16: disclosed: Public disclosure
- 2026-09-16: patched: Fixed in BIND 9.20.29 and 9.20.29-S1

## References

- [https://downloads.isc.org/isc/bind9/9.20.29](https://downloads.isc.org/isc/bind9/9.20.29)
- [https://kb.isc.org/docs/cve-2026-19662](https://kb.isc.org/docs/cve-2026-19662)

## Related threats

- [BIND assertion failure with redirect zone and qname-minimization](https://junglewise.ai/threats/cve-2026-96888-a-bind-resolver-that-is-configured-with-both-a-redirect-zone-and)
- [BIND named GSS-TSIG replay heap corruption](https://junglewise.ai/threats/cve-2026-94300-replaying-gss-tsig-signed-udp-messages-can-result-in-memory)
- [ISC BIND resolver DNS message processing denial of service](https://junglewise.ai/threats/cve-2026-19630-in-a-bind-resolver-inbound-dns-protocol-messages-with-a)
- [ISC BIND denial of service via TKEY queries](https://junglewise.ai/threats/cve-2015-5477-isc-bind-data-processing-errors-vulnerability)
- [BIND resolver crash on DNSSEC-signed wildcard with NSEC mismatch](https://junglewise.ai/threats/cve-2026-80274-bind-resolver-crash-on-dnssec-signed-wildcard-with-nsec-mismatch)