Resolver crash via unchecked NSEC cache cast
Published Apr 22, 2026 · Updated Apr 22, 2026
Denial of service in PowerDNS Recursor 5.2.0 through 5.2.8, 5.3.0 through 5.3.5, and 5.4.0 allows remote attackers to crash the resolver. During getDenial processing, aggressive_nsec.cc casts a cached candidate to an NSEC record without handling a type change during an NSEC-to-NSEC3 transition, leaving a null result for later use. An unauthenticated attacker must control a DNSSEC zone and time the transition during denial-proof processing; the result is a resolver crash with no reported system compromise.
Summary
What happened
Denial of service in PowerDNS Recursor 5.2.0 through 5.2.8, 5.3.0 through 5.3.5, and 5.4.0 allows remote attackers to crash the resolver. During getDenial processing, aggressive_nsec.cc casts a cached candidate to an NSEC record without handling a type change during an NSEC-to-NSEC3 transition, leaving a null result for later use. An unauthenticated attacker must control a DNSSEC zone and time the transition during denial-proof processing; the result is a resolver crash with no reported system compromise.
The record
- CVE
- CVE-2026-33261
- Published
- Apr 22, 2026
- Updated
- Apr 22, 2026
- Vendor
- PowerDNS
- Product
- PowerDNS Recursor
- Classifications
- CWE-353, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 22, 2026CVE publishedPublication date reported by the CVE source.
- Apr 22, 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 <5.2.9
- Affected versionversion=5.3.0 <5.3.6
- Affected versionversion=5.4.0 <5.4.1
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
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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