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CVE-2026-40209— Denial of service via IXFR queries

Quick assessment

Affected
PowerDNS DNSdist
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

PowerDNS dnsdist是PowerDNS公司开源的一款高性能DNS流量分发与防护工具。 PowerDNS DNSdist存在资源管理错误漏洞，该漏洞源于IXFR查询处理问题，可能导致后端TCP连接超时，在连接数限制或文件描述符不足时造成拒绝服务。以下版本受到影响：1.9.0版本至1.9.15之前版本，2.0.0版本至2.0.7之前版本。

CVSS 5.3 · Medium EPSS 0.70% · P52

Affected Version Matrix 2

VendorProduct Version RangeStatus
PowerDNS DNSdist 1.9.0< 1.9.15 affected
2.0.0< 2.0.7 affected
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I. Basic Information for CVE-2026-40209

Vulnerability Information
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Vulnerability Title
Denial of service via IXFR queries
Source: CVE Program / CVE List V5
Vulnerability Description
An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
PowerDNS DNSdist 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
PowerDNS dnsdist是PowerDNS公司开源的一款高性能DNS流量分发与防护工具。 PowerDNS DNSdist存在资源管理错误漏洞，该漏洞源于IXFR查询处理问题，可能导致后端TCP连接超时，在连接数限制或文件描述符不足时造成拒绝服务。以下版本受到影响：1.9.0版本至1.9.15之前版本，2.0.0版本至2.0.7之前版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
PowerDNS DNSdist 1.9.0 ~ 1.9.15 -

II. Public POCs for CVE-2026-40209

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III. Intelligence Information for CVE-2026-40209

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Vendor Advisories for CVE-2026-40209 (1)

Same Patch Batch · PowerDNS · 2026-06-25 · 14 CVEs total

CVE-2026-33612 7.5 HIGH ZoneToCache can poison the cache
CVE-2026-42387 5.9 MEDIUM Insufficient input validation in ZoneToCache
CVE-2026-42388 5.9 MEDIUM Missing input validation for catalog zones
CVE-2026-52690 5.9 MEDIUM Spoofed answers can mark an authoritative non-EDNS capable
CVE-2026-42390 5.3 MEDIUM ZONEMD validation can be bypassed
CVE-2026-42389 5.3 MEDIUM Reject more queries with invalid header values
CVE-2026-40211 5.3 MEDIUM Denial of service via crafted DoH3 queries
CVE-2026-40012 5.3 MEDIUM Information about ECS zero scoped answers might leak to clients that use a specific ECS
CVE-2026-40210 4.8 MEDIUM Out-of-bounds read in SetMacAddrAction
CVE-2026-42005 4.3 MEDIUM Insufficient input validation of internal web server
CVE-2026-42004 3.7 LOW EDNS options smuggling
CVE-2026-40011 3.7 LOW Prometheus denial of service via crafted DNS queries
CVE-2026-40208 3.7 LOW Denial of service via DoH3 queries

IV. Related Vulnerabilities

Same product: DNSdist
Same vendor: PowerDNS

V. Comments for CVE-2026-40209

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