CVE-2026-11721 (GCVE-0-2026-11721)
Vulnerability from cvelistv5 – Published: 2026-07-22 14:13 – Updated: 2026-07-22 18:52
VLAI
EPSS
VEX
Title
Cache poisoning possible with label count discrepancy, RRSIG, and wildcards
Summary
It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-22 18:52 UTC
CWE
- CWE-1284 - Improper Validation of Specified Quantity in Input
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://kb.isc.org/docs/cve-2026-11721 | vendor-advisory |
| https://downloads.isc.org/isc/bind9/9.20.26 | patch |
| https://downloads.isc.org/isc/bind9/9.21.24 | patch |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| ISC | BIND 9 |
Affected:
9.11.0 , ≤ 9.18.50
(custom)
Affected: 9.20.0 , ≤ 9.20.24 (custom) Affected: 9.21.0 , ≤ 9.21.23 (custom) Affected: 9.11.3-S1 , ≤ 9.18.50-S1 (custom) Affected: 9.20.9-S1 , ≤ 9.20.24-S1 (custom) cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* |
Date Public
2026-07-22 00:00
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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