CVE-2025-40777— A possible assertion failure when 'stale-answer-client-timeout' is set to '0'
Quick assessment
Affected
ISC BIND 9
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
ISC BIND 9是ISC组织的一个域名系统软件。 ISC BIND 9存在安全漏洞，该漏洞源于断言失败，可能导致服务中止。以下版本受到影响：9.20.0至9.20.10版本、9.21.0至9.21.9版本和9.20.9-S1至9.20.10-S1版本。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2025-40777
Vulnerability Information
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Vulnerability Title
A possible assertion failure when 'stale-answer-client-timeout' is set to '0'
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
可达断言
Source: CVE Program / CVE List V5
Vulnerability Title
ISC BIND 9 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ISC BIND 9是ISC组织的一个域名系统软件。 ISC BIND 9存在安全漏洞，该漏洞源于断言失败，可能导致服务中止。以下版本受到影响：9.20.0至9.20.10版本、9.21.0至9.21.9版本和9.20.9-S1至9.20.10-S1版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2025-40777
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IV. Related Vulnerabilities
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V. Comments for CVE-2025-40777
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