CVE-2025-40775

DNS message with invalid TSIG causes an assertion failure

Severity Score

7.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Attend

*SSVC

Descriptions

When an incoming DNS protocol message includes a Transaction Signature (TSIG), BIND always checks it. If the TSIG contains an invalid value in the algorithm field, BIND immediately aborts with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.8 and 9.21.0 through 9.21.7.

When an incoming DNS protocol message includes a Transaction Signature (TSIG), BIND always checks it. If the TSIG contains an invalid value in the algorithm field, BIND immediately aborts with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.8 and 9.21.0 through 9.21.7.

It was discovered that Bind incorrectly handled certain DNS messages with invalid TSIG. A remote attacker could possibly use this issue to cause Bind to crash, resulting in a denial of service.

*Credits: N/A

CVSS Scores

Internet Systems Consortium (ISC)v3.1 7.5
Tenablev2 7.8

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Attack Vector

Network

Attack Complexity

Low

Authentication

None

Confidentiality

None

Integrity

None

Availability

Complete

* Common Vulnerability Scoring System

SSVC

Decision:Attend

Exploitation

None

Automatable

Yes

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2025-04-16 CVE Reserved
2025-05-21 CVE Published
2025-05-23 CVE Updated
2025-05-29 First Exploit
2025-07-16 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date

CWE

CWE-232: Improper Handling of Undefined Values

CAPEC

References (2)

URL	Tag	Source

URL	Date	SRC
https://github.com/AlexSvobo/nhi-zero-trust-bypass	2025-05-29

URL	Date	SRC

URL	Date	SRC
https://kb.isc.org/docs/cve-2025-40775	2025-05-21

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
ISC Search vendor "ISC"		BIND 9 Search vendor "ISC" for product "BIND 9"				>= 9.20.0 <= 9.20.8 Search vendor "ISC" for product "BIND 9" and version " >= 9.20.0 <= 9.20.8"		en		Affected
ISC Search vendor "ISC"		BIND 9 Search vendor "ISC" for product "BIND 9"				>= 9.21.0 <= 9.21.7 Search vendor "ISC" for product "BIND 9" and version " >= 9.21.0 <= 9.21.7"		en		Affected