# CVE-2026-77119: ISC BIND DNSSEC validation bypass with NSEC3 forgery

Source: https://junglewise.ai/threats/cve-2026-77119-isc-bind-dnssec-validation-bypass-with-nsec3-forgery  
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-2026-77119 · Severity: medium · CVSS 5.9 · Published 2026-09-16

BIND is a widely-used DNS server responsible for translating domain names into IP addresses. A flaw in DNSSEC validation allows a forged NSEC3 record from an unrelated domain zone to be accepted as proof of insecurity, potentially allowing attackers to downgrade a secure delegation and serve forged DNS responses. This could redirect users to malicious websites or intercept network traffic.

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

## Quick answers

**Is CVE-2026-77119 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77119 being exploited in the wild.

**How severe is CVE-2026-77119?** 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, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

**Is there a fix for CVE-2026-77119?** A patch was published on 2026-09-16: Fixed in BIND 9.20.29 and 9.21.26 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77119 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-77119?** 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 DNSSEC validation flaw in BIND's NSEC3 processing logic. An attacker can craft a validly signed NSEC3 record from an unrelated sibling zone and present it as proof of non-existence (an insecurity proof), causing the resolver to incorrectly downgrade a secure delegation to an insecure one. This allows the attacker to serve forged unsigned DNS answers that would normally be rejected by DNSSEC validation. The attack requires network access to the resolver and does not require authentication, though successful exploitation depends on proper DNSSEC signing in the attacker-controlled zone. Patches are available in BIND 9.20.29 and 9.21.26 (released 2026-09-16).

## 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, and 9.20.9-S1 through 9.20.27-S1

## Timeline

- 2026-09-16: disclosed
- 2026-09-16: patched: Fixed in BIND 9.20.29 and 9.21.26

## 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)