CVE-2026-5950
Unbounded resend loop in BIND 9 resolver
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.
INFO
Published Date :
May 20, 2026, 1:16 p.m.
Last Modified :
May 21, 2026, 3:24 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update BIND 9 to a patched version.
- Review BIND 9 documentation for specific fixes.
- Monitor server resources after applying updates.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-5950.
| URL | Resource |
|---|---|
| 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 |
| https://kb.isc.org/docs/cve-2026-5950 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-5950 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-5950
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-5950 vulnerability anywhere in the article.
-
CybersecurityNews
BIND 9 Software Vulnerabilities Exposes Resolvers and Authoritative Servers to Remote Exploits
A series of newly documented vulnerabilities in ISC BIND 9 has raised significant security concerns for DNS infrastructure operators, with multiple flaws enabling denial-of-service (DoS) attacks, memo ... Read more
The following table lists the changes that have been made to the
CVE-2026-5950 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 21, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.18.36 up to (excluding) 9.18.49 *cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.20.8 up to (excluding) 9.20.23 *cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.21.7 up to (excluding) 9.21.21 Added Reference Type Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.18.49 Types: Patch Added Reference Type Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.20.23 Types: Patch Added Reference Type Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.21.22 Types: Patch Added Reference Type Internet Systems Consortium (ISC): https://kb.isc.org/docs/cve-2026-5950 Types: Vendor Advisory -
New CVE Received by [email protected]
May. 20, 2026
Action Type Old Value New Value 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-606 Added Reference https://downloads.isc.org/isc/bind9/9.18.49 Added Reference https://downloads.isc.org/isc/bind9/9.20.23 Added Reference https://downloads.isc.org/isc/bind9/9.21.22 Added Reference https://kb.isc.org/docs/cve-2026-5950