CVE-2026-5950 (GCVE-0-2026-5950)
Vulnerability from cvelistv5 – Published: 2026-05-20 13:10 – Updated: 2026-05-20 13:38
VLAI
EPSS
VEX
Title
Unbounded resend loop in BIND 9 resolver
Summary
An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions.
This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.
Severity
5.3 (Medium)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-20 13:38 UTC
CWE
- CWE-606 - Unchecked Input for Loop Condition
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://kb.isc.org/docs/cve-2026-5950 | vendor-advisory |
| https://downloads.isc.org/isc/bind9/9.18.49 | patch |
| https://downloads.isc.org/isc/bind9/9.20.23 | patch |
| https://downloads.isc.org/isc/bind9/9.21.22 | patch |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| ISC | BIND 9 |
Affected:
9.18.36 , ≤ 9.18.48
(custom)
Affected: 9.20.8 , ≤ 9.20.22 (custom) Affected: 9.21.7 , ≤ 9.21.21 (custom) Affected: 9.18.36-S1 , ≤ 9.18.48-S1 (custom) Affected: 9.20.9-S1 , ≤ 9.20.22-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
2026-05-20 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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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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.