CVE-2025-40777

7.5 highEPSS 1.0%

High (7.5). EPSS 1.0% chance of exploitation in the next 30 days.

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.

Severity

CVSS 3.1

7.5 high

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

EPSS: 1.0% chance of exploitation in the next 30 days; higher than 63% of CVEs (scores of 2026-10-31)
CWE: CWE-617
Published: 2025-07-16
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

References

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

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