CVE-2025-40775: ISC BIND 9

High severity, CVSS 7.5. EPSS: 15.2% chance of exploitation in the next 30 days.

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.

Affected products

• ISC BIND 9: from 9.20.0, up to and including 9.20.8; from 9.21.0, up to and including 9.21.7

Published 2025-05-21. Last modified 2026-06-17.