Denial of service via oversized NSEC cache entries
Published Apr 22, 2026 · Updated Apr 22, 2026
Resource exhaustion 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 interrupt DNS service. Crafted DNS responses from an attacker-published zone make the negative and aggressive NSEC(3) caches allocate entries without an effective size limit. Exploitation requires control of a DNS zone and queries that cause the Recursor to process its responses; the resulting memory growth interrupts availability without system compromise.
Summary
What happened
Resource exhaustion 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 interrupt DNS service. Crafted DNS responses from an attacker-published zone make the negative and aggressive NSEC(3) caches allocate entries without an effective size limit. Exploitation requires control of a DNS zone and queries that cause the Recursor to process its responses; the resulting memory growth interrupts availability without system compromise.
The record
- CVE
- CVE-2026-33258
- Published
- Apr 22, 2026
- Updated
- Apr 22, 2026
- Vendor
- PowerDNS
- Product
- PowerDNS Recursor
- Classifications
- CWE-770, T1499.002
- 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?
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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