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CVE-2025-40777

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CVE-2025-40777

Published: Jul 16, 2025

Modified: Nov 4, 2025

PUBLISHED

CVSS v3.1

7.5

HIGH

Description

If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.

VendorProductVersions

ISC

BIND 9

affected
9.20.0 - <= 9.20.10
affected
9.21.0 - <= 9.21.9
affected
9.20.9-S1 - <= 9.20.10-S1
unaffected
9.18.0 - <= 9.18.37
unaffected
9.18.11-S1 - <= 9.18.37-S1

Weaknesses (CWE)

CWE-617

CVSS v3.1 Details

CVSS v3.1 Vector

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

References

CVE-2025-40777
vendor-advisory

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