CVE-2026-116205 in YesWiki
Summary
by MITRE • 10/25/2026
YesWiki before 4.7.0 contains an unauthenticated server-side request forgery vulnerability that allows remote attackers to fetch arbitrary URLs by supplying [[|URL]] wiki syntax to the render handler. Attackers can pass the syntax in the content parameter of the page render handler to reach internal hosts and ports and read their responses.
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Analysis
by VulDB Data Team • 10/25/2026
YesWiki versions prior to 4.7.0 are susceptible to an unauthenticated server-side request forgery vulnerability within its rendering engine. This flaw arises from improper validation of user-supplied input when processing wiki syntax, specifically the double-bracket notation used for linking or embedding content. The render handler fails to adequately sanitize URLs provided in this format, allowing remote attackers without any form of authentication to inject arbitrary Uniform Resource Locators into server-side requests. By supplying a maliciously crafted [[|URL]] structure within the content parameter passed to the page render handler, an attacker can compel the YesWiki application to initiate HTTP requests on their behalf. This capability effectively turns the vulnerable web application into a proxy or relay for network reconnaissance and data exfiltration activities.
The technical mechanism of this vulnerability relies on the server's ability to resolve and fetch external resources as part of its normal rendering process. When an attacker provides a URL pointing to internal infrastructure, such as private IP addresses or localhost endpoints, the server processes this request internally rather than displaying it merely as text. This behavior enables attackers to probe internal networks that are typically isolated from direct internet access. By analyzing the HTTP responses returned by these internal services, attackers can identify running services, detect open ports, and potentially retrieve sensitive data such as configuration files or API responses. The lack of authentication means this vector is accessible to any user with view permissions on a wiki page, significantly lowering the barrier for exploitation compared to authenticated attacks.
From an operational perspective, this vulnerability poses severe risks related to internal network discovery and potential further compromise. Attackers can use this flaw to map out the organization's internal topology, identifying critical systems such as databases, administrative interfaces, or other microservices that are not exposed publicly but may have their own vulnerabilities. The ability to read responses from these internal hosts allows for detailed fingerprinting of software versions and configurations, which facilitates targeted attacks against those specific services. In environments where sensitive data is stored in local applications accessible only via localhost, this vulnerability could lead to direct exposure of confidential information without the need for bypassing firewalls or network segmentation controls designed to protect such assets from external access.
This issue aligns with CWE-918, which classifies Server-Side Request Forgery (SSRF) flaws where a web application fetches a remote resource without validating the user-supplied URL. It also maps directly to MITRE ATT&CK technique T1571, specifically the Proxy Connection subcategory, as attackers leverage the vulnerable server to establish connections with internal resources that would otherwise be unreachable from the internet. The unauthenticated nature of this exploit further exacerbates its severity under common vulnerability scoring systems due to the ease of access and potential for widespread impact across any deployment using affected versions.
To mitigate this risk, organizations running YesWiki must immediately upgrade to version 4.7.0 or later where these input validation checks have been implemented. Until an upgrade is feasible, administrators should consider implementing strict web application firewall rules that block outbound requests from the server to private IP address ranges such as RFC 1918 addresses unless explicitly required for business operations. Additionally, restricting wiki editing permissions and ensuring that only trusted users can modify page content can reduce the attack surface by limiting who can inject malicious syntax into the render handler. Regular security audits of template rendering logic are also recommended to prevent similar SSRF vectors in other parts of the application infrastructure.