Medium 5.3Published May 20, 2026

CVE-2026-5950Unbounded resend loop in BIND 9 resolver

Updated under an hour ago (Oct 26, 2026, 12:20 AM ET)

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It affects ISC BIND 9 and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for ISC BIND 9

Exploited in the last 30 days

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.

CVSS: 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-606
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: isc
NVD analysis: Analyzed
Record last updated: May 20, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

ISC BIND 9 isc:bind_9 (from the name)	from 9.18.36 through 9.18.48; from 9.20.8 through 9.20.22; from 9.21.7 through 9.21.21; from 9.18.36-S1 through 9.18.48-S1; from 9.20.9-S1 through 9.20.22-S1	CNA record
isc bind isc:bind	from 9.18.36 before 9.18.49; from 9.20.8 before 9.20.23; from 9.21.7 before 9.21.21	NVD

References

https://kb.isc.org/docs/cve-2026-5950vendor-advisory
https://downloads.isc.org/isc/bind9/9.18.49patch
https://downloads.isc.org/isc/bind9/9.20.23patch
https://downloads.isc.org/isc/bind9/9.21.22patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.