CVE-2025-30195 Overview
CVE-2025-30195 is a Null Pointer Dereference vulnerability affecting PowerDNS Recursor that allows remote attackers to cause a denial of service condition. An attacker can publish a DNS zone containing specific Resource Record Sets that, when processed and cached by the Recursor, trigger illegal memory accesses leading to a crash.
This vulnerability affects the core DNS resolution functionality, making it particularly concerning for organizations relying on PowerDNS Recursor for DNS infrastructure. The attack can be executed remotely over the network without requiring any authentication or user interaction.
Critical Impact
Remote attackers can crash PowerDNS Recursor instances by publishing malicious DNS zones, causing service disruption to all dependent DNS resolution services.
Affected Products
- PowerDNS Recursor versions prior to 5.2.1
Discovery Timeline
- 2025-04-07 - CVE CVE-2025-30195 published to NVD
- 2025-04-07 - Last updated in NVD database
Technical Details for CVE-2025-30195
Vulnerability Analysis
This vulnerability is classified as CWE-476 (NULL Pointer Dereference), a memory corruption issue that occurs when the application attempts to use a pointer that is expected to be valid but is actually NULL. In the context of PowerDNS Recursor, the vulnerability manifests during the processing and caching of specially crafted Resource Record Sets.
When the Recursor encounters these malicious DNS records, the parsing or caching logic fails to properly validate pointer references before dereferencing them. This results in an illegal memory access that causes the Recursor process to crash, effectively denying DNS resolution services to all clients depending on the affected instance.
The attack is particularly effective because it exploits normal DNS resolution behavior—the Recursor will naturally attempt to process any records it receives while performing recursive lookups.
Root Cause
The root cause is improper handling of pointer validation during Resource Record Set processing. The code path responsible for caching DNS query results contains a condition where a NULL pointer can be dereferenced, likely due to missing validation checks when handling edge cases in specific RRset configurations.
Attack Vector
The attack vector is network-based and does not require authentication or user interaction. An attacker executes this attack by:
- Setting up a malicious DNS zone under their control
- Crafting specific Resource Record Sets designed to trigger the vulnerability
- Inducing the target PowerDNS Recursor to query the malicious zone (either directly or through recursive resolution)
- The Recursor processes the malicious records, triggering the NULL pointer dereference
- The Recursor crashes, causing denial of service
The vulnerability affects the availability of the DNS service. For technical implementation details, see the PowerDNS Security Advisory 2025-01.
Detection Methods for CVE-2025-30195
Indicators of Compromise
- Unexpected PowerDNS Recursor process crashes or restarts
- Core dump files indicating NULL pointer dereference in RRset processing functions
- Elevated crash rates correlating with queries to specific external DNS zones
- Segmentation fault errors in system logs related to the pdns_recursor process
Detection Strategies
- Monitor PowerDNS Recursor process stability using process supervision tools (systemd, supervisord)
- Implement DNS query logging to identify suspicious patterns of queries to unusual or newly registered domains
- Deploy crash monitoring to detect abnormal process termination events
- Analyze core dumps for NULL pointer dereference signatures in DNS record processing code paths
Monitoring Recommendations
- Configure alerting on PowerDNS Recursor service restarts or crashes
- Monitor system logs for segmentation fault or illegal memory access messages from pdns_recursor
- Track DNS resolution latency anomalies that may indicate service disruption
- Implement health checks that verify DNS resolution functionality is operational
How to Mitigate CVE-2025-30195
Immediate Actions Required
- Upgrade PowerDNS Recursor to version 5.2.1 or later immediately
- Review PowerDNS Recursor logs for any evidence of crashes or exploitation attempts
- Ensure automatic service restart is configured to minimize downtime in case of crashes
- Consider implementing rate limiting on recursive queries to reduce attack surface
Patch Information
The vulnerability has been remediated in PowerDNS Recursor version 5.2.1. Organizations should upgrade to this patched version as the primary mitigation strategy.
For detailed patch information and upgrade instructions, refer to the PowerDNS Security Advisory 2025-01.
Additional disclosure information is available via the Openwall OSS Security Post.
Workarounds
- Implement process monitoring with automatic restart capabilities to minimize service disruption during exploitation attempts
- Deploy redundant DNS resolver infrastructure to maintain availability if one instance is targeted
- Consider using DNS firewall or RPZ (Response Policy Zones) to block queries to known malicious domains
- Monitor for and block traffic patterns associated with exploitation attempts at the network perimeter
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
