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CVE-2025-30194: DNSdist Denial of Service Vulnerability via nghttp2 Provider

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Overview

The CVE-2025-30194 vulnerability pertains to DNSdist, a highly DNS, DoS, and abuse-aware load balancer. When configured to provide DNS over HTTPS (DoH) via the nghttp2 provider, it is susceptible to an attack that can trigger an illegal memory access (double-free) and crash of DNSdist. This results in a denial of service, potentially compromising the system or leading to data leakage. It’s of critical importance due to its high severity score and the potential for system-wide impacts.

Vulnerability Summary

CVE ID: CVE-2025-30194
Severity: High (7.5 CVSS score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage

Affected Products

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Product | Affected Versions

DNSdist | All versions before 1.9.9

How the Exploit Works

The exploit works by an attacker crafting a DNS over HTTPS (DoH) exchange that triggers an illegal memory access (double-free) in DNSdist. This causes a crash of DNSdist, leading to a denial of service. This can potentially compromise the system or lead to data leakage.

Conceptual Example Code

Given that the nature of this exploit is DNS-based and not typically linked with a distinct payload, a conceptual example of how this vulnerability might be exploited is not straightforward. However, the attack would likely involve a maliciously crafted DNS query sent over HTTPS, which would be designed to trigger the illegal memory access.

POST /dns-query HTTP/1.1
Host: vulnerable-dnsdist.example.com
Content-Type: application/dns-message
{ "malicious_dns_query": "..." }

Remediation

The recommended remediation is to upgrade DNSdist to the patched version 1.9.9. As a temporary workaround, users can switch to the h2o provider until DNSdist has been upgraded to a fixed version. Alternatively, apply a vendor patch or use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as temporary mitigation.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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