Medium severity · published May 20, 2026
CVE-2026-5950
Unbounded resend loop in BIND 9 resolver
5.3
CVSS
0.7%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 51% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
B9
BIND 9 · ISC
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; 9.20.9-S1 through 9.20.22-S1 · source: vendor
BI
Bind · Isc
9.18.36 before 9.18.49; 9.20.8 before 9.20.23; 9.21.7 before 9.21.21 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5950
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-5950
Patch
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
Vendor Advisory
https://kb.isc.org/docs/cve-2026-5950
More from BIND 9
9.8
CVE-2026-3593
Heap use-after-free vulnerability in BIND 9 DNS-over-HTTPS implementation
8.6
CVE-2026-13321
DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field
8.1
CVE-2026-94300
Concurrent GSS-TSIG messages corrupt memory
7.8
CVE-2017-3141
Windows service and uninstall paths are not quoted when BIND is installed
7.5
CVE-2026-97313
Specific RPZ configurations and query patterns may result in an unexpected exit