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HIGH

CVE-2025-40775

DNS message with invalid TSIG causes an assertion failure

CVSS v3

7.5

HIGH

EPSS Score

15.2 %

exploit probability, as of 2026-09-25

CISA KEV

No

known exploited

Exploitation

none

SSVC status

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.

Technical details

Published
2025-05-21
Last Modified
2026-04-15

Frequently asked questions

What is CVE-2025-40775?

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.

Is CVE-2025-40775 actively exploited?

Active exploitation of CVE-2025-40775 has not been confirmed. Its EPSS score was 15.2% on 2026-09-25, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-40775?

CVE-2025-40775 has a CVSS v3 base score of 7.5 (HIGH severity).

Is CVE-2025-40775 affecting your environment?

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