# CVE-2026-19630: ISC BIND resolver DNS message processing denial of service

Source: https://junglewise.ai/threats/cve-2026-19630-in-a-bind-resolver-inbound-dns-protocol-messages-with-a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-19630 · Severity: high · CVSS 7.5 · Published 2026-10-21

BIND is a widely-used DNS resolver that processes incoming DNS queries from networks. A specially crafted DNS message with a malicious structure can force BIND to consume excessive CPU and memory, making the DNS service unavailable to legitimate users. An attacker on the network can trigger this condition without authentication, causing denial of service.

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

## Quick answers

**Is CVE-2026-19630 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19630 being exploited in the wild.

**How severe is CVE-2026-19630?** High severity, with a CVSS score of 7.5, published 21 October 2026.

**Which products and versions are affected?** Isc Bind 9.11.0–9.18.50, 9.20.0–9.20.29, 9.21.0–9.21.26, 9.11.3-S1–9.18.50-S1, 9.20.9-S1–9.20.29-S1.

**Is there a fix for CVE-2026-19630?** Yes: fixed in BIND 9.18.51, 9.20.30, 9.21.27, 9.18.51-S1, 9.20.30-S1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-19630 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-19630?** 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.

## How to fix

- Fixed in BIND 9.18.51, 9.20.30, 9.21.27, 9.18.51-S1, 9.20.30-S1

## Technical details

The vulnerability is an algorithmic complexity flaw in BIND's DNS message parsing: inbound DNS protocol messages containing a particular structure are processed without limits, allowing an attacker to craft a message with a large number of such structures to trigger disproportionate resource consumption. The attack requires only network access to the resolver (UDP/TCP port 53) and no authentication. A successful exploit denies DNS resolution service.

## Affected products

- ISC BIND 9.11.0–9.18.50, 9.20.0–9.20.29, 9.21.0–9.21.26, 9.11.3-S1–9.18.50-S1, 9.20.9-S1–9.20.29-S1

## Timeline

- 2026-10-21: disclosed

## References

- [https://downloads.isc.org/isc/bind9/9.20.30](https://downloads.isc.org/isc/bind9/9.20.30)
- [https://downloads.isc.org/isc/bind9/9.21.27](https://downloads.isc.org/isc/bind9/9.21.27)

## 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 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)
- [ISC BIND DNSSEC validation bypass with NSEC3 forgery](https://junglewise.ai/threats/cve-2026-77119-isc-bind-dnssec-validation-bypass-with-nsec3-forgery)