Executive Summary

CVE-2026-7724 is a DNS rebinding Time-of-Check Time-of-Use (TOCTOU) vulnerability in the validate_restricted_url function of the PrefectHQ prefect project. The vulnerability arises because the function initially resolves a hostname to an IP address and checks if it is private, but then passes the original hostname to the HTTP client, which re-resolves the DNS at connection time. This gap allows an attacker-controlled DNS server to return a public IP during validation and a private IP during the actual connection, bypassing Server-Side Request Forgery (SSRF) protections.

Additionally, the original function only checked the first DNS A record, allowing mixed public and private DNS responses to bypass validation. The vulnerability can be exploited remotely but requires high complexity and is considered difficult to exploit.

The fix involves hardening the validation function to check all resolved addresses, introducing protected HTTP transports that prevent DNS re-resolution by connecting directly to validated IPs, and updating webhook components to use these protections.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can allow an attacker to bypass SSRF protections and potentially make the application send requests to internal or private network resources that should be inaccessible. This could lead to unauthorized access to internal services, data leakage, or other security breaches within the network.

Because the attack exploits DNS rebinding and TOCTOU timing issues, it can be used to manipulate the target system into connecting to unintended internal IP addresses, which might expose sensitive information or allow further exploitation.

Useful 0 Not Useful 0

Detection Guidance

This vulnerability involves a DNS rebinding Time-of-Check Time-of-Use (TOCTOU) bypass in the validate_restricted_url function, which is difficult to detect directly on a network or system due to its high complexity and the nature of DNS resolution timing.

Detection would involve monitoring for unusual DNS resolution patterns or unexpected DNS responses that switch between public and private IP addresses for the same hostname.

Since the vulnerability exploits DNS rebinding, you can use network tools to monitor DNS queries and responses, for example:

• Use tcpdump or Wireshark to capture DNS traffic and look for multiple IP addresses returned for the same hostname within a short time frame.
• Example tcpdump command: tcpdump -i any port 53 -w dns_capture.pcap
• Use dig or nslookup repeatedly to query the hostname used by the Prefect webhook to see if DNS responses vary between public and private IPs.
• Example dig command: dig example-hostname.com +short

However, no specific detection commands or tools are provided in the available resources or CVE description.

Useful 0 Not Useful 0

Mitigation Strategies

The primary and recommended mitigation step is to upgrade Prefect to version 3.6.28.dev2 or later, which includes the fix for this vulnerability.

The fix hardens the validate_restricted_url function to validate all resolved IP addresses and introduces protected HTTP transports that prevent DNS rebinding attacks by connecting directly to pre-validated IP addresses.

Upgrading ensures that the vulnerability is addressed by eliminating the time-of-check time-of-use window exploited by attackers.

No other immediate mitigation steps such as configuration changes or workarounds are mentioned in the provided resources.

Useful 0 Not Useful 0

Compliance Impact

The provided information does not include any details on how the CVE-2026-7724 vulnerability affects compliance with common standards and regulations such as GDPR or HIPAA.

Useful 0 Not Useful 0