CVE-2026-5950

🔶 medium

Summary

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 Score

5.3

Medium

EPSS Score

0.1

Exploit Probability

Published Date

2026-05-20

First Seen: 2026-05-21

📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 19.7% of all 329,778 vulnerabilities in our database.

#264,886

Below average severity

Severity Percentile

🎯 CISA SSVC Assessment Updated: May 20, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

YES

Can be exploited automatically

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

ISC would like to thank Billy Baraja (BielraX) for bringing this vulnerability to our attention.

SSVC data provided by CISA

Last Modified 2026-05-21

Source NVD 🔗

CVSS Vector 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CWE IDs (Weakness Types)

CWE-606

📦 Affected Products 3

Vendor	Product	Status	Affected Versions
isc	bind	Affected	> 9.18.36 < 9.18.49
isc	bind	Affected	> 9.20.8 < 9.20.23
isc	bind	Affected	> 9.21.7 < 9.21.21

🔗 References 4

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

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-3039	⚠️ high	7.5	0.1	BIND servers that are configured to use TKEY-based authentication via GSS-API tokens are vulnerable to excessive memory ...	2026-05-20
CVE-2026-3592	🔶 medium	5.3	0.0	BIND resolvers are vulnerable to an amplified resource consumption/exhaustion attack. If a victim resolver makes a quer...	2026-05-20
CVE-2026-3593	⚠️ high	7.4	0.0	A use-after-free vulnerability exists within the DNS-over-HTTPS implementation. This issue affects BIND 9 versions 9.20....	2026-05-20
CVE-2026-5946	⚠️ high	7.5	0.1	Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`...	2026-05-20
CVE-2026-5947	⚠️ high	7.5	0.0	Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incomi...	2026-05-20
CVE-2026-1519	⚠️ high	7.5	0.1	If a BIND resolver is performing DNSSEC validation and encounters a maliciously crafted zone, the resolver may consume e...	2026-03-25

These CVEs affect the same products