Client-specific DNS answer disclosure via improper caching
Published Jun 25, 2026 · Updated Jun 25, 2026
Information disclosure in affected PowerDNS Recursor releases allows remote attackers to receive cached ECS scope-zero answers. The packet cache incorrectly stores scope-zero responses and later returns them to clients that present a specific EDNS Client Subnet. The issue is reachable only when ECS is enabled; it exposes DNS answer information without enabling service interruption or system compromise.
Summary
What happened
Information disclosure in affected PowerDNS Recursor releases allows remote attackers to receive cached ECS scope-zero answers. The packet cache incorrectly stores scope-zero responses and later returns them to clients that present a specific EDNS Client Subnet. The issue is reachable only when ECS is enabled; it exposes DNS answer information without enabling service interruption or system compromise.
The record
- CVE
- CVE-2026-40012
- Published
- Jun 25, 2026
- Updated
- Jun 25, 2026
- Vendor
- PowerDNS
- Product
- PowerDNS Recursor
- Classifications
- CWE-668, CWE-524
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 25, 2026CVE publishedPublication date reported by the CVE source.
- Jun 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=5.2.0 <5.2.11
- Affected versionversion=5.3.0 <5.3.8
- Affected versionversion=5.4.0 <5.4.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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