CVE-2026-46556 in FlaskBB
Summary
by MITRE • 07/22/2026
FlaskBB is a Forum Software written in Python using the micro framework Flask. Prior to version 2.2.1, a Server-Side Request Forgery (SSRF) vulnerability in get_image_info() allows any authenticated user to force the server to send HTTP requests to arbitrary internal endpoints, including cloud metadata services. This is a blind SSRF with confirmed internal port scanning and internal API triggering capabilities. Version 2.2.1 patches the issue.
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Analysis
by VulDB Data Team • 07/22/2026
FlaskBB represents a popular forum software implementation built upon the Flask microframework architecture, serving as a collaborative platform for community discussions and content sharing. The vulnerability under examination affects versions prior to 2.2.1 and stems from improper input validation within the get_image_info() function that processes image metadata requests. This flaw enables authenticated users to manipulate the application's behavior by crafting specially formatted requests that bypass normal access controls and routing mechanisms.
The technical implementation of this server-side request forgery vulnerability occurs through the get_image_info() method which accepts user-provided URLs without adequate sanitization or validation. When an authenticated user submits a request containing a malicious URL, the application attempts to fetch image metadata from the specified endpoint without proper authorization checks or network boundary enforcement. This creates an attack surface where internal network resources become accessible through the vulnerable application layer, effectively transforming the web server into a proxy for internal network reconnaissance and exploitation.
The operational impact of this blind SSRF vulnerability extends beyond simple information disclosure to encompass comprehensive internal network mapping capabilities. Attackers can leverage this flaw to perform port scanning activities against internal services that would otherwise be protected by network segmentation and firewalls. The vulnerability's confirmed ability to trigger internal API endpoints demonstrates the severity of potential consequences, as it could enable access to sensitive internal systems including cloud metadata services that contain critical infrastructure information such as instance IDs, security credentials, and network configurations. This capability fundamentally undermines the application's security posture and exposes organizations to significant risk.
The remediation implemented in version 2.2.1 addresses this vulnerability through proper input validation and URL sanitization mechanisms within the get_image_info() function. Security patches typically involve implementing strict validation of user-provided URLs, enforcing whitelist-based access controls for external resources, and ensuring that internal network endpoints remain isolated from user-controllable application inputs. Organizations should prioritize immediate deployment of the patched version while also implementing additional monitoring and logging mechanisms to detect potential exploitation attempts. This vulnerability aligns with CWE-918 which specifically addresses server-side request forgery conditions and demonstrates how authenticated access can be leveraged to bypass network security controls, a pattern frequently documented in ATT&CK framework under techniques related to internal reconnaissance and privilege escalation through application vulnerabilities.
The broader implications of this flaw highlight the critical importance of input validation in web applications, particularly those handling user-provided resources such as image URLs or external content. Organizations utilizing FlaskBB or similar frameworks must conduct comprehensive security assessments to identify similar vulnerabilities across their application portfolios, focusing on functions that process external inputs and interact with network resources. Implementation of network segmentation, proper access controls, and regular vulnerability scanning practices becomes essential in mitigating the risk associated with such server-side request forgery conditions that can effectively transform legitimate application functionality into attack vectors for internal network reconnaissance and exploitation.