# CVE-2026-19667: ISC BIND named negative cache denial of service

Source: https://junglewise.ai/threats/cve-2026-19667-isc-bind-named-negative-cache-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-2026-19667 · Severity: high · CVSS 7.5 · Published 2026-09-16

BIND is a widely-deployed DNS server that resolves domain names for millions of users and organizations. An attacker running an authoritative DNS server can craft a specially-sized response (exactly 65536 bytes) that causes BIND to create a corrupted cache entry. When BIND later tries to read this entry, the server crashes, causing DNS resolution to fail for affected customers.

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

## Quick answers

**Is CVE-2026-19667 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19667 being exploited in the wild.

**How severe is CVE-2026-19667?** High severity, with a CVSS score of 7.5, 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, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.27-S1.

**Is there a fix for CVE-2026-19667?** A patch was published on 2026-09-16: BIND 9.20.29 and 9.21.26 released with fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-19667 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-19667?** 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 denial-of-service flaw in the negative cache handling logic of BIND's `named` resolver. When an attacker-controlled authoritative DNS server responds with a negative answer (NXDOMAIN or NODATA) that is exactly 65536 bytes in size, a bug in the cache entry creation causes the negative cache entry to be allocated with 0 bytes. Subsequently, when `named` attempts to read this malformed cache entry, it triggers an abort condition. The attack requires the victim to query a domain controlled by an attacker; no authentication is required. Patches are available in BIND 9.20.29, 9.21.26, and later versions.

## Affected products

- ISC BIND 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.27-S1

## Timeline

- 2026-09-16: disclosed: CVE-2026-19667 published
- 2026-09-16: patched: BIND 9.20.29 and 9.21.26 released with fix

## References

- [https://downloads.isc.org/isc/bind9/9.20.29](https://downloads.isc.org/isc/bind9/9.20.29)
- [https://downloads.isc.org/isc/bind9/9.21.26](https://downloads.isc.org/isc/bind9/9.21.26)

## 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)