CVE-2026-104440 in YesWiki
Summary
by MITRE • 10/02/2026
YesWiki before 4.6.7 contains a blind server-side request forgery vulnerability that allows unauthenticated attackers to make arbitrary server-side requests via the idtypeannonce parameter of /api/entries/bazarlist. Because isValidURL() always returns true, attackers can supply internal URLs fetched by curl in loadURLContent() to probe internal networks and reach internal services or metadata endpoints.
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Analysis
by VulDB Data Team • 10/02/2026
YesWiki versions prior to 4.6.7 are susceptible to a critical blind server-side request forgery vulnerability located within the /api/entries/bazarlist endpoint. This flaw is specifically triggered by improper validation of input passed through the idtypeannonce parameter, allowing unauthenticated attackers to manipulate the backend application into making arbitrary HTTP requests on their behalf. The core technical deficiency lies in the implementation of the isValidURL() function, which fails to enforce strict schema or domain restrictions and instead returns true for virtually any provided string value. This permissive validation logic effectively bypasses standard security controls designed to prevent SSRF attacks by allowing attackers to inject internal IP addresses, localhost references, or cloud metadata service endpoints directly into the request flow.
Once a malicious payload is submitted via the idtypeannonce parameter, it is passed to the loadURLContent() function which utilizes curl to fetch the content of the specified URL. Because the initial validation step does not filter out private network ranges or internal hostnames, the server proceeds to execute the HTTP request using its own identity and network privileges. This capability enables attackers to perform reconnaissance against internal infrastructure that is otherwise inaccessible from the public internet. By analyzing the response behavior or timing differences in a blind SSRF scenario, an attacker can probe for open ports, identify running services such as databases or administrative panels, and potentially exfiltrate sensitive data stored on local servers without triggering immediate alerts due to the lack of direct feedback mechanisms in many server configurations.
The operational impact of this vulnerability extends beyond simple network probing. Attackers can leverage this flaw to access internal metadata endpoints commonly found in cloud environments, such as AWS EC2 instance metadata or Azure managed identity tokens, potentially leading to full compromise of underlying infrastructure if combined with other exploitation techniques. Furthermore, the ability to reach internal services allows for further lateral movement within a segmented network environment. Since the vulnerability is unauthenticated, any user visiting the affected page or sending an API request can exploit this flaw without needing valid credentials, significantly lowering the barrier to entry for malicious actors and increasing the likelihood of successful attacks in public-facing deployments.
From a classification perspective, this issue aligns with CWE-918 Server-Side Request Forgery (SSRF), specifically highlighting failures in input validation and URL parsing logic that permit internal network access. In terms of adversary tactics, this vulnerability facilitates reconnaissance activities categorized under the MITRE ATT&CK technique T1572 Protocol Tunneling or potentially T1046 Network Service Discovery if used to map out internal services. To mitigate this risk, developers must implement strict allow-lists for URLs that can be fetched by loadURLContent(), ensuring only whitelisted domains are permitted. Additionally, integrating a robust URL validation library that checks against private IP ranges and loopback addresses is essential. Deploying network-level controls such as firewall rules to restrict outbound connections from the web server application tier to internal resources provides an additional layer of defense in depth, limiting the blast radius even if the application-layer vulnerability persists.