CVE-2026-104463 in YesWiki
Summary
by MITRE • 10/02/2026
YesWiki before 4.6.7 contains a server-side request forgery vulnerability that allows unauthenticated attackers to trigger server requests by sending signed Follow activities to the public forms actor inbox route. Attackers sign requests with their own keyId while supplying internal actor URLs in the body, reaching internal hosts or cloud metadata via blind GET and POST requests.
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Analysis
by VulDB Data Team • 10/02/2026
The security flaw identified in YesWiki versions prior to 4.6.7 represents a critical server-side request forgery vulnerability that exploits the application's handling of ActivityPub protocol activities. Specifically, the defect resides within the public forms actor inbox route, which is designed to receive and process Follow activities from other federated instances or actors. The core technical issue stems from insufficient validation of the source identity associated with these incoming requests. An unauthenticated attacker can craft a malicious Follow activity where they sign the request using their own keyId but manipulate the body content to include URLs pointing to internal network resources or cloud metadata services. Because the application processes this signed payload without adequately verifying that the requested resource is external and safe, it proceeds to execute HTTP GET and POST requests on behalf of the server itself.
This vulnerability allows for blind SSRF attacks where the attacker does not necessarily receive a direct response from the targeted internal service but can still cause the YesWiki server to interact with restricted network segments. By supplying internal actor URLs or IP addresses in the body, attackers can probe internal infrastructure, access cloud metadata endpoints such as those found on AWS EC2 instances which often contain sensitive credentials and configuration data, or reach other services running on localhost that are not exposed to the public internet. The ability to send both GET and POST requests expands the potential impact beyond simple information disclosure, enabling actions like authentication bypasses against internal APIs, denial of service through resource exhaustion, or further exploitation if an internal service has its own vulnerabilities.
From a classification perspective, this vulnerability aligns with CWE-918 Server-Side Request Forgery (SSRF), specifically involving the lack of restrictions on server-side network connections initiated by user-controlled data. In terms of offensive security frameworks, it maps to MITRE ATT&CK technique T1571 which covers Non-Standard Ports and potentially T1046 Network Service Discovery if used for internal reconnaissance. The attack vector is particularly dangerous because it leverages the legitimate ActivityPub protocol mechanisms, making the malicious traffic appear as standard federated social media interactions rather than obvious exploitation attempts. This obscurity can allow the vulnerability to persist undetected by basic network monitoring tools that do not inspect application-layer payload contents deeply.
The operational impact of this flaw is significant for any deployment of YesWiki that exposes its public forms actor inbox route, which is common in federated setups. Attackers with no prior authentication can compromise the integrity and confidentiality of the hosting environment. If deployed within a cloud infrastructure, successful exploitation could lead to the theft of instance metadata credentials, granting attackers full control over the virtual machine or access to other services via shared roles. In on-premises deployments, it may allow lateral movement across internal networks by accessing administrative interfaces of routers, printers, or database servers that are not firewalled off from the web server.
Mitigation strategies must focus on strict input validation and network-level controls. The primary remediation is to upgrade YesWiki to version 4.6.7 or later where this logic has been corrected to properly validate the origin of requests and restrict allowed destinations for internal processing. Until an upgrade can be performed, administrators should implement web application firewall rules that block outbound connections from the server to private IP ranges such as RFC1918 addresses unless explicitly required by business logic. Additionally, configuring network segmentation so that the YesWiki instance cannot directly access sensitive internal services or cloud metadata endpoints provides a critical layer of defense in depth. Monitoring logs for unusual outbound connection patterns initiated by the web application process can also aid in early detection of exploitation attempts.