CVE-2026-72591 in Koito
Summary
by MITRE • 08/10/2026
A server-side request forgery (SSRF) vulnerability in gabehf/Koito through v0.3.2 allows an authenticated user to make the server perform HTTP requests to arbitrary internal or external hosts by supplying a crafted image_url value in the PATCH /apis/web/v1/album/{id}/image endpoint. The application fetches the supplied URL server-side without validating the destination host or blocking access to private, loopback, link-local, or internal addresses.
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability represents a critical server-side request forgery flaw in the gabehf/Koito application affecting versions through v0.3.2. The issue manifests through the PATCH /apis/web/v1/album/{id}/image endpoint where authenticated users can manipulate the image_url parameter to force the server into making HTTP requests to arbitrary destinations. The vulnerability stems from inadequate input validation and sanitization mechanisms within the application's request handling pipeline, allowing malicious actors to bypass normal network restrictions and access internal resources that should remain protected.
The technical implementation of this vulnerability follows a classic SSRF pattern where the application acts as an intermediary between external users and internal systems without proper boundary enforcement. When an authenticated user submits a crafted image_url value, the server performs a direct HTTP request to the specified endpoint without validating whether the destination address falls within acceptable network ranges. This includes private IP address spaces such as 10.x.x.x, 172.16.x.x through 172.31.x.x, and 192.168.x.x ranges, as well as loopback addresses like 127.0.0.1 and IPv6 equivalents. The absence of proper host validation creates an attack surface where internal systems become accessible to authenticated users who should not have direct network access.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable lateral movement within internal networks and privilege escalation attacks. An attacker with valid credentials could leverage this flaw to probe internal services, potentially accessing databases, application servers, or other sensitive internal resources that are normally protected by network segmentation. This capability aligns with attack techniques described in the MITRE ATT&CK framework under T1071.004 for application layer protocol and T1566 for credential access through social engineering. The vulnerability essentially transforms a legitimate image upload feature into a reconnaissance and exploitation tool that can bypass traditional network security controls.
Security implications become particularly severe when considering that the vulnerability affects an authenticated endpoint, meaning attackers only need valid user credentials to exploit the flaw rather than requiring initial access through other attack vectors. This makes the vulnerability more accessible and dangerous in environments where credential compromise is possible through phishing or other social engineering techniques. The impact on organizational security posture can be substantial as it allows for internal network mapping, service enumeration, and potential data exfiltration from systems that are supposed to be isolated from external access.
Organizations should implement comprehensive mitigations including strict input validation, host allowlists or denylists, network segmentation controls, and proper URL sanitization techniques. The solution architecture must enforce network boundary checks at the application level rather than relying on network-level firewalls alone. Implementing a whitelist approach that only permits specific domains or IP ranges to be accessed through the application's image fetching capability provides the most effective defense against this class of vulnerability. Additionally, adopting security controls aligned with CWE-918 server-side request forgery standards and implementing proper access controls through authentication and authorization frameworks will significantly reduce the risk exposure associated with this vulnerability.