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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
ISC BIND 9 unaffected
Version Status Constraints
9.18.36 affected ≤ 9.18.48
9.20.8 affected ≤ 9.20.22
9.21.7 affected ≤ 9.21.21
9.18.36-S1 affected ≤ 9.18.48-S1
9.20.9-S1 affected ≤ 9.20.22-S1

No data.

No data.

No data.

Project Subscriptions

Vendors Products
Isc Subscribe
Bind Subscribe
Advisories

No advisories yet.

Fixes

Solution

Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.49, 9.20.23, 9.21.22, 9.18.49-S1, or 9.20.23-S1.

Workaround

No workarounds known.

References
Link Providers
https://downloads.isc.org/isc/bind9/9.18.49 cve-icon cve-icon
https://downloads.isc.org/isc/bind9/9.20.23 cve-icon cve-icon
https://downloads.isc.org/isc/bind9/9.21.22 cve-icon cve-icon
https://kb.isc.org/docs/cve-2026-5950 cve-icon cve-icon
History

Wed, 20 May 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 20 May 2026 13:15:00 +0000

Type Values Removed Values Added
Description 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.
Title Unbounded resend loop in BIND 9 resolver
First Time appeared Isc
Isc bind
Weaknesses CWE-606
CPEs cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
Vendors & Products Isc
Isc bind
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: isc

Published:

Updated: 2026-05-20T13:38:53.211Z

Reserved: 2026-04-09T06:42:23.953Z

Link: CVE-2026-5950

cve-icon Vulnrichment

Updated: 2026-05-20T13:38:44.672Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-20T13:16:40.450

Modified: 2026-05-20T14:04:57.320

Link: CVE-2026-5950

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses