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

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.

Published: 2025-07-16 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-40776 is rated Low Risk (39.7/100): CVSS High severity, with low exploitation likelihood (EPSS 0.24%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-40776

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.01% 0.24% +0.23%
2 2025-07-17 — 0.01% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-40776

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 4.0 [email protected]

Weakness enumeration for CVE-2025-40776

OS Trackers for CVE-2025-40776

vendor priority summary link
alpine high CVE-2025-40776: 1 source package rows (bind); 2 state rows across 2 repos (3.22-main, edge-main); fixed 2, open 0. https://security.alpinelinux.org/vuln/CVE-2025-40776
debian unimportant CVE-2025-40776 unimportant priority: Debian including 1 source packages (bind9), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-40776
suse high CVE-2025-40776 severity important: SUSE including 32 source package names (bind, bind-chrootenv, …), 216 product×package rows across 35 product lines (SLES-LTSS-TERADATA 15 SP2, SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS, … (35 product lines)): Known Not Affected 216. https://www.suse.com/security/cve/CVE-2025-40776/
ubuntu medium CVE-2025-40776 medium priority: Ubuntu including 3 source packages (bind9, bind9-libs, isc-dhcp), 21 status rows across 8 suites (bionic, focal, jammy, noble, plucky, trusty, upstream, xenial): not-affected 17, DNE 2, needs-triage 2. https://ubuntu.com/security/CVE-2025-40776

Affected software / configurations for CVE-2025-40776

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-40776

cvelogic Threat Intelligence