What’s Vulnerable › Vulnerabilities

CVE-2025-40776: Birthday Attack against Resolvers supporting ECS

• Severity: high (CVSS 8.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-07-16 · updated 2026-06-17
• Weakness: CWE-349

Description

A `named` caching resolver that is configured to send ECS (EDNS Client Subnet) options may be vulnerable to a cache-poisoning attack. This issue affects BIND 9 versions 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.37-S1, and 9.20.9-S1 through 9.20.10-S1.

Affected products

• ISC BIND: from 9.11.3-S1 through 9.16.50-S1; from 9.18.11-S1 through 9.18.37-S1; from 9.20.9-S1 through 9.20.10-S1

References

• https://kb.isc.org/docs/cve-2025-40776

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