CVE-2026-33611 Overview
CVE-2026-33611 is an Integer Overflow vulnerability affecting PowerDNS Authoritative Server. An operator with REST API access can cause the Authoritative server to produce invalid HTTPS or SVCB record data, which can subsequently lead to LMDB database corruption when using the LMDB backend.
Critical Impact
Authenticated attackers with REST API privileges can corrupt the LMDB database backend, potentially causing loss of data integrity and service availability for DNS operations.
Affected Products
- PowerDNS Authoritative Server (versions using LMDB backend)
- PowerDNS installations with REST API enabled
- Systems utilizing HTTPS or SVCB DNS record types
Discovery Timeline
- 2026-04-22 - CVE CVE-2026-33611 published to NVD
- 2026-04-22 - Last updated in NVD database
Technical Details for CVE-2026-33611
Vulnerability Analysis
This vulnerability stems from CWE-190 (Integer Overflow or Wraparound) in the PowerDNS Authoritative Server's handling of HTTPS and SVCB record data through the REST API. When an authenticated operator submits specially crafted record data via the REST API, the server fails to properly validate numeric boundaries, resulting in an integer overflow condition.
The overflow causes the generation of invalid HTTPS or SVCB DNS record data. When this malformed data is written to the LMDB (Lightning Memory-Mapped Database) backend, it corrupts the database structure. LMDB is a memory-mapped B+ tree database that provides efficient read operations for DNS lookups, making corruption particularly impactful for DNS service availability.
The attack requires network access and high privileges (REST API operator credentials), but once those conditions are met, no user interaction is required to exploit the vulnerability. The impact is primarily on integrity and availability of the DNS service, with no direct confidentiality impact.
Root Cause
The root cause is an Integer Overflow (CWE-190) in the record data processing logic. When handling HTTPS or SVCB record parameters through the REST API, the server performs arithmetic operations on user-supplied values without adequate boundary checking. This allows numeric values to wrap around when they exceed the maximum representable value, producing unexpected and invalid record data that violates LMDB storage constraints.
Attack Vector
The attack is network-based and requires an authenticated operator with REST API access. The attacker submits malformed HTTPS or SVCB record data through the REST API endpoints, triggering the integer overflow condition during record processing. The corrupted data is then persisted to the LMDB backend, potentially rendering the DNS database unusable.
The vulnerability specifically targets the SVCB (Service Binding) and HTTPS record types, which are relatively newer DNS record types used for service discovery and HTTPS connection optimization. The attacker crafts parameter values designed to trigger integer overflow during the record serialization process.
Detection Methods for CVE-2026-33611
Indicators of Compromise
- Unexpected LMDB database corruption errors in PowerDNS logs
- Abnormal REST API requests containing malformed HTTPS or SVCB record data
- Integer overflow-related error messages in server logs
- DNS service failures following REST API administrative operations
Detection Strategies
- Monitor PowerDNS REST API access logs for unusual HTTPS or SVCB record creation requests
- Implement input validation alerts for record data with extreme numeric values
- Set up LMDB database integrity monitoring with regular consistency checks
- Configure alerting for REST API authentication from unexpected sources
Monitoring Recommendations
- Enable detailed logging for all REST API operations on PowerDNS servers
- Implement regular automated database integrity verification for LMDB backends
- Monitor for service restarts or crashes following administrative API operations
- Track REST API operator activity patterns for anomalous behavior
How to Mitigate CVE-2026-33611
Immediate Actions Required
- Review and restrict REST API access to trusted operators only
- Audit current REST API operator accounts and remove unnecessary privileges
- Implement network-level controls to limit REST API access to authorized management networks
- Create verified backups of LMDB databases before applying any patches
Patch Information
Refer to the PowerDNS Security Advisory for official patch information and updated software versions. Organizations should apply vendor-provided patches as soon as they become available after appropriate testing.
Workarounds
- Disable REST API access if not required for operations
- Implement strict network segmentation for REST API management interfaces
- Consider using alternative database backends (non-LMDB) if available and appropriate for your environment
- Apply additional input validation at the network perimeter for API requests
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
