# CVE-2026-75029: ISC BIND DNS cache memory exhaustion in query responses

Source: https://junglewise.ai/threats/cve-2026-75029-isc-bind-dns-cache-memory-exhaustion-in-query-responses  
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-2026-75029 · Severity: medium · CVSS 5.3 · Published 2026-09-16

BIND is a widely-deployed DNS resolver software used by organizations to translate domain names to IP addresses. An attacker can send specially-crafted DNS responses containing duplicate records (like SOA records) to exhaust the resolver's memory through its negative cache, potentially causing performance degradation or service unavailability.

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

## Quick answers

**Is CVE-2026-75029 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-75029 being exploited in the wild.

**How severe is CVE-2026-75029?** Medium severity, with a CVSS score of 5.3, 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-2026-75029?** A patch was published on 2026-09-16: BIND 9.18.51, 9.20.28, and 9.21.26 released with fixes Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-75029 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-75029?** 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

A flaw in BIND's DNS query response handling allows an attacker to send multiple copies of records that should exist only once (e.g., SOA records) in a single response. When the RDATA (resource record data) is identical across all copies, BIND appends each record to its in-memory negative cache instead of deduplicating, leading to unbounded memory growth. This is a network-reachable vulnerability requiring no authentication; an attacker can repeatedly send malicious responses to trigger memory exhaustion. The vulnerability affects BIND 9.11.0–9.18.50, 9.20.0–9.20.27, 9.21.0–9.21.25, and their -S1 (FIPS) variants. Patches are available in BIND 9.18.51+, 9.20.28+, and 9.21.26+.

## 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-2026-75029 published
- 2026-09-16: patched: BIND 9.18.51, 9.20.28, and 9.21.26 released with fixes

## 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)