CVE-2025-40776
CSIRTS triage
- What
- A birthday attack against DNS resolvers supporting EDNS Client Subnet (ECS) extension allows cache poisoning or service disruption.
- Who is affected
- Authoritative and recursive DNS resolvers with ECS support enabled globally.
- Urgency
- High severity (CVSS 8.6) due to significant attack potential against critical DNS infrastructure.
- Action
- Disable ECS if not required, or update resolver to patched version implementing birthday attack mitigations.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.20% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 10% of all EPSS-scored CVEs.
Advisory coverage (1)
- highCVE-2025-40776: Birthday Attack against Resolvers supporting ECSmsrc · 2026-08-06
External references
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