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CVE-2025-40777

A possible assertion failure when 'stale-answer-client-timeout' is set to '0'

Published: Jul 16, 2025Updated: Nov 4, 2025 Sources: CVE List NVDCWE-617
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.9%
Top 45.7%
CISA KEV
Not in KEV
Exploits
0 Known
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-617

Affected Products

BIND 9ISCNetworking Infrastructure
isccommercialUSNetworking Infrastructureaka internet systems consortium

Attack Graph

Products CVE Techniques Tactics

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Exploitability

0 exploit sources identified

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Official Patch Available
Workaround Available

MITRE ATT&CK

1 technique
Impact
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References

https://kb.isc.org/docs/cve-2025-40777
kb.isc.org
http://www.openwall.com/lists/oss-security/2025/07/16/6
openwall.com

Timeline

Published
Jul 16, 2025
Last Updated
Nov 4, 2025

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