SecuriTricks - CVE-2025-40777

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.

Product(s) Impacted

Vendor	Product	Versions
Isc	Bind	9.20.0-9.20.10, 9.21.0-9.21.9, 9.20.9-S1-9.20.10-S1

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-617

Reachable Assertion

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

*CPE(s)

Affected systems and software identified for this CVE.

Type	Vendor	Product	Version	Update	Edition	Language	Software Edition	Target Software	Target Hardware	Other Information
a	isc	bind	9.20.0-9.20.10	/	/	/	/	/	/	/
a	isc	bind	9.21.0-9.21.9	/	/	/	/	/	/	/
a	isc	bind	9.20.9-S1-9.20.10-S1	/	/	/	/	/	/	/

References

https://kb.isc.org/docs/cve-2025-40777

CVSS Score

7.5 / 10

CVSS Data - 3.1

Attack Vector: NETWORK
Attack Complexity: LOW
Privileges Required: NONE
Scope: UNCHANGED
Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: HIGH

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

View Vector String

Timeline

Published: July 16, 2025, 6:15 p.m.
Last Modified: July 17, 2025, 9:15 p.m.

Status : Awaiting Analysis

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

security-officer@isc.org

CVE-2025-40777