CVE-2025-40775

DNS message with invalid TSIG causes an assertion failure

Description

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.

Remediation

Solution:

  • Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.9 or 9.21.8.

Workaround:

  • No workarounds known.

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
EPSS 0.02%
Vendor Advisory isc.org
Affected: ISC BIND 9
Published at:
Updated at:

References

Link Tags
https://kb.isc.org/docs/cve-2025-40775 vendor advisory
http://www.openwall.com/lists/oss-security/2025/05/21/1
https://security.netapp.com/advisory/ntap-20250523-0001/

Frequently Asked Questions

What is the severity of CVE-2025-40775?
CVE-2025-40775 has been scored as a high severity vulnerability.
How to fix CVE-2025-40775?
To fix CVE-2025-40775: Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.9 or 9.21.8.
Is CVE-2025-40775 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2025-40775 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-40775?
CVE-2025-40775 affects ISC BIND 9.
This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.
© 2025 Under My Watch. All Rights Reserved.