High severity · published Jul 16, 2025
CVE-2025-40776
Birthday Attack against Resolvers supporting ECS
8.6
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 14% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
B9
BIND 9 · ISC
9.11.3-S1 through 9.16.50-S1; 9.18.11-S1 through 9.18.37-S1; 9.20.9-S1 through 9.20.10-S1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-40776
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-40776
kb.isc.org
https://kb.isc.org/docs/cve-2025-40776
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