# CVE-2026-3039: ISC BIND 9 memory exhaustion in GSS-API TKEY negotiation

Source: https://junglewise.ai/threats/cve-2026-3039-isc-bind-9-memory-exhaustion-in-gss-api-tkey-negotiation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-20. Updated: 2026-05-20  
License: CC BY 4.0 with a link back

CVE-2026-3039 · Severity: high · CVSS 7.5 · Published 2026-05-20

BIND is a widely used software for managing Domain Name System (DNS) services, often integrated with Active Directory or Kerberos environments. A vulnerability exists where an attacker can send specially crafted network packets that cause the server to consume excessive amounts of memory without releasing it. If left unaddressed, this can lead to a complete service outage, preventing users from accessing websites or internal network resources.

Technologies: [Isc BIND 9](https://junglewise.ai/threats/technologies/bind-9), [Isc BIND 9 Supported Preview Edition](https://junglewise.ai/threats/technologies/bind-9-supported-preview-edition). Vendors: [Isc](https://junglewise.ai/threats/vendors/isc).

## Quick answers

**Is CVE-2026-3039 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-3039 being exploited in the wild.

**How severe is CVE-2026-3039?** High severity, with a CVSS score of 7.5, published 20 May 2026.

**Which products and versions are affected?** Isc BIND 9 9.0.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21; Isc BIND 9 Supported Preview Edition 9.9.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, 9.20.9-S1 through 9.20.22-S1.

**Is there a fix for CVE-2026-3039?** A patch was published on 2026-05-20: Patched versions released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-3039 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-3039?** Check whether you run Isc BIND 9 or Isc BIND 9 Supported Preview Edition 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 memory leak vulnerability (CWE-771) exists in BIND 9 when processing TKEY-based authentication via GSS-API tokens. The root cause is a failure to release allocated memory when receiving maliciously constructed packets during GSS-API TKEY negotiation. This is a remote, unauthenticated attack vector that allows an attacker to trigger excessive memory consumption. Over time, or with sufficient volume, the 'named' process will exhaust available system memory and fail, resulting in a denial of service. Patches are available in versions 9.18.49, 9.20.23, and 9.21.22.

## Affected products

- ISC BIND 9 9.0.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21
- ISC BIND 9 Supported Preview Edition 9.9.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, 9.20.9-S1 through 9.20.22-S1

## Timeline

- 2026-05-13: other: Early notification provided
- 2026-05-20: advisory: Public disclosure by ISC
- 2026-05-20: patched: Patched versions released

## References

- [https://downloads.isc.org/isc/bind9/9.18.49](https://downloads.isc.org/isc/bind9/9.18.49)
- [https://downloads.isc.org/isc/bind9/9.20.23](https://downloads.isc.org/isc/bind9/9.20.23)
- [https://downloads.isc.org/isc/bind9/9.21.22](https://downloads.isc.org/isc/bind9/9.21.22)
- [https://kb.isc.org/docs/cve-2026-3039](https://kb.isc.org/docs/cve-2026-3039)

## Related threats

- [ISC BIND recursive server assert failure denial of service](https://junglewise.ai/threats/cve-2026-97313-a-recursive-bind-server-that-receives-a-query-with-recursion)
- [ISC BIND DNSSEC validation bypass in NSEC records](https://junglewise.ai/threats/cve-2026-13321-isc-bind-dnssec-validation-bypass-in-nsec-records)
- [ISC BIND 9 denial of service via NSEC and NSEC3 assertion failure](https://junglewise.ai/threats/cve-2026-13204-isc-bind-9-denial-of-service-via-nsec-and-nsec3-assertion-failure)
- [ISC BIND 9 denial of service via CNAME or DNAME record ordering](https://junglewise.ai/threats/cve-2026-12617-isc-bind-9-denial-of-service-via-cname-or-dname-record-ordering)
- [ISC BIND 9 cache poisoning via RRSIG label count discrepancy](https://junglewise.ai/threats/cve-2026-11721-isc-bind-9-cache-poisoning-via-rrsig-label-count-discrepancy)