CVE-2026-110628 in Kan
Summary
by MITRE • 10/14/2026
Kan 0.5.5 through 0.6.0 contains an unauthenticated server-side request forgery vulnerability in the /api/download/attatchment route due to an incomplete fix for CVE-2026-32255. When S3_ENDPOINT is unset, attackers can pass arbitrary url query parameters to fetch() to read internal services, localhost ports, and cloud instance metadata.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified in Kan versions 0.5.5 through 0.6.0 represents a critical server-side request forgery flaw located within the /api/download/attachment endpoint. This issue stems from an incomplete remediation of CVE-2026-32255, indicating that previous security patches failed to fully address the underlying logic error in how external URLs are processed. The core technical deficiency lies in the application's handling of URL parameters when the S3_ENDPOINT environment variable is not configured or remains unset. In this specific configuration state, the server fails to properly validate or sanitize user-supplied input before passing it to internal fetch operations. This lack of rigorous validation allows an unauthenticated attacker to inject arbitrary URLs into the request flow, effectively turning the application into a proxy for malicious network requests.
From a technical perspective, this vulnerability exploits the trust relationship between the backend server and its surrounding infrastructure. By manipulating query parameters that are forwarded to the underlying HTTP client library, attackers can direct the Kan instance to initiate connections to internal services that are not exposed to the public internet. This includes accessing localhost ports running on the same host or within the local network segment, as well as querying cloud provider metadata endpoints such as those found in AWS EC2 Instance Metadata Service (IMDS) or Azure Managed Identity endpoints. The ability to read these internal resources allows an attacker to gather sensitive configuration data, authentication tokens, and other credentials that are typically stored in environment variables or instance metadata stores for ease of access by running applications.
The operational impact of this vulnerability is severe due to the unauthenticated nature of the exploit. An adversary does not need valid login credentials to initiate these requests, significantly lowering the barrier to entry for exploitation. Once an attacker successfully leverages this flaw, they can achieve several malicious outcomes. They may exfiltrate sensitive data from internal microservices that rely on Kan as a gateway or proxy. More critically, by accessing cloud instance metadata, attackers can retrieve temporary security credentials, such as AWS IAM role session tokens or Azure managed identity access tokens. These credentials often have broader permissions than the application itself, potentially allowing for lateral movement within the network, privilege escalation to administrative levels, and full compromise of the underlying infrastructure. This scenario aligns with common attack patterns observed in cloud-native environments where misconfigured proxies facilitate unauthorized data retrieval from internal endpoints.
This vulnerability maps directly to CWE-918, Server-Side Request Forgery (SSRF), specifically involving unvalidated user input leading to access control bypasses and information disclosure. It also correlates with MITRE ATT&CK technique T1504, Web Service Discovery, as the attacker uses the application to probe for internal services, and potentially T1537, Transfer Data to Cloud Account, if exfiltrated data is sent to an external server controlled by the attacker. The incomplete fix nature of this issue highlights a common pitfall in security patching where partial remediation leaves residual attack vectors active under specific configuration states.
To mitigate this risk, immediate action is required for all systems running Kan versions 0.5.5 through 0.6.0. The most effective mitigation involves upgrading to the latest patched version of Kan that fully addresses CVE-2026-32255 and its associated SSRF flaws. If an upgrade is not immediately feasible, administrators should ensure that the S3_ENDPOINT environment variable is explicitly set to a valid internal or external endpoint, thereby bypassing the code path vulnerable to arbitrary URL injection. Additionally, implementing network-level controls such as firewall rules or security group policies can restrict outbound traffic from Kan instances to only allow connections to known and trusted domains. Blocking access to cloud metadata endpoints at the network perimeter provides an additional layer of defense against SSRF-based credential theft. Regular vulnerability scanning and penetration testing should be conducted to identify similar misconfigurations in other services that may act as proxies for internal resources.