CVE-2026-63088 in stoatchat
Summary
by MITRE • 07/16/2026
stoatchat before 0.14.0 contains a server-side request forgery (SSRF) vulnerability that allows unauthenticated network-accessible attackers to bypass the DNS-based IP blocklist by exploiting incomplete address validation in the url_is_blacklisted function, which inspects only the first resolved address while the underlying HTTP client iterates all cached addresses.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/16/2026
The stoatchat application version 0.14.0 and earlier contains a critical server-side request forgery vulnerability that fundamentally undermines network security controls. This flaw exists within the url_is_blacklisted function implementation where the system performs incomplete address validation by inspecting only the first resolved IP address from DNS queries. The vulnerability arises from a mismatch between the application's filtering logic and how underlying HTTP clients handle cached network addresses, creating a dangerous gap in network access control mechanisms.
The technical exploitation of this vulnerability occurs through manipulation of DNS resolution behavior where attackers can craft malicious URLs that initially resolve to whitelisted addresses but subsequently iterate through cached addresses that may contain blacklisted IP ranges. The url_is_blacklisted function fails to account for the fact that HTTP clients typically attempt connections to all resolved addresses in a cache, not just the first one returned by DNS resolution. This incomplete validation creates an attack surface where network requests can bypass security measures designed to block specific IP ranges or domains.
From an operational perspective this vulnerability allows unauthenticated attackers with network access to potentially circumvent IP-based blacklisting controls that are fundamental to preventing access to malicious or unauthorized resources. The impact extends beyond simple bypass of firewall rules to potentially enable access to internal systems, data exfiltration, or further attack vector exploitation. Attackers can leverage this weakness to probe internal networks, access restricted services, or perform reconnaissance activities that would normally be blocked by the application's security controls.
The vulnerability demonstrates a classic flaw in input validation and address resolution handling that aligns with CWE-918 Server-Side Request Forgery (SSRF) classification under the broader category of insecure data validation. This weakness creates opportunities for attackers to exploit incomplete address validation mechanisms, representing a significant gap in the application's security architecture. The issue also maps to ATT&CK technique T1190 for exploitation of remote services and T1071.004 for application layer protocol usage, highlighting how this vulnerability can be leveraged as part of broader attack chains.
Mitigation strategies should focus on implementing comprehensive address validation that considers all resolved addresses rather than just the first one returned by DNS resolution. The application should validate against all IP addresses in the resolved set and ensure proper handling of DNS cache behavior to prevent bypass attempts. Additionally, network-level controls such as egress filtering and proper firewall rules should be implemented to reduce the impact of potential exploitation. Regular security updates and code reviews focusing on address validation patterns are essential for preventing similar vulnerabilities in future releases.