CVE-2026-73058 in stoatchat
Summary
by MITRE • 08/16/2026
stoatchat versions before 0.15.0 fail to block the IPv6 unspecified address (::) in the SSRF blocklist, allowing unauthenticated attackers to bypass protections via the /proxy and /embed endpoints. Attackers can craft requests using IPv6 literal syntax to access services on the loopback interface and retrieve sensitive internal content.
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Analysis
by VulDB Data Team • 08/16/2026
The vulnerability identified in stoatchat versions prior to 0.15.0 represents a critical server-side request forgery flaw rooted in an incomplete input validation mechanism within the application's proxying logic. Specifically, the security controls designed to prevent unauthorized access to internal resources failed to recognize and block the IPv6 unspecified address, commonly referred to as :: or all-zeros. This oversight allows unauthenticated attackers to circumvent existing SSRF protections by leveraging specific IPv6 literal syntax in their requests directed at the /proxy and /embed endpoints. The root cause lies in a gap within the allowlist or denylist implementation that processes destination addresses, where the logic did not adequately map this particular address format to blocked entries, thereby permitting traffic destined for local interfaces to pass through the application's filtering layer.
From an operational perspective, this flaw enables attackers to interact with services running on the loopback interface of the server hosting stoatchat. By crafting requests that resolve or specify the IPv6 unspecified address, adversaries can reach internal applications, databases, or administrative panels that are not exposed to external networks but remain accessible locally. This capability facilitates the retrieval of sensitive internal content, such as configuration files, session tokens, database credentials, or proprietary data stored within backend services. The impact is severe because it effectively neutralizes network-level isolation strategies that rely on restricting access from public-facing interfaces while allowing local communication for performance or security reasons. Attackers can use this vector to pivot further into the internal network topology, potentially leading to full system compromise if combined with other vulnerabilities in connected services.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-918, which describes Server-Side Request Forgery (SSRF) flaws where server-side code makes requests from a back-end machine and trusts user-supplied input without sufficient validation. Additionally, the exploitation technique maps to MITRE ATT&CK tactic T1059, specifically Command and Scripting Interpreter or Network Service Discovery depending on the payload used, but more accurately fits under reconnaissance techniques that involve probing internal network resources via forged requests. The failure to block a well-known reserved address indicates a deficiency in defensive coding practices regarding IP address parsing and normalization.
To mitigate this vulnerability, it is imperative for administrators of stoatchat instances running versions before 0.15.0 to upgrade immediately to the patched release where the SSRF blocklist has been corrected to include the IPv6 unspecified address and other related loopback variants such as ::1 or fe80::1 depending on implementation specifics. In environments where upgrading is not immediately feasible, network-level controls should be implemented to restrict outbound traffic from the stoatchat server's IP address to only necessary external endpoints, effectively creating a whitelist approach for egress filtering. Furthermore, application firewalls can be configured to inspect and drop requests containing IPv6 literal syntax that target local subnets or reserved addresses, providing an additional layer of defense against SSRF attempts until the software patch is applied.