CVE-2026-5950

Unbounded resend loop in BIND 9 resolver

Published May 20, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor 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.


Vendor Workaround

No workarounds known.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4725-1 bind9 security update
Debian DSA Debian DSA DSA-6285-1 bind9 security update
Ubuntu USN Ubuntu USN USN-8293-1 Bind vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
Type Values Removed Values Added
Metrics ssvc

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
isc
Published
Updated
May 20, 2026, 1:38 PM
Reserved
Apr 9, 2026, 6:42 AM
Status
Analyzed
Published
May 20, 2026, 1:16 PM
Modified
Jul 23, 2026, 12:10 PM
Severity
Moderate
Public date
May 26, 2026, 3:43 AM