CVE-2026-39989 in Download Station
Summary
by MITRE • 10/15/2026
A server-side request forgery (SSRF) vulnerability has been reported to affect Download Station. If a remote attacker gains a user account, they can then exploit the vulnerability to read application data.
We have already fixed the vulnerability in the following version: Download Station 5.10.1.312 and later Download Station 5.11.2.321 and later
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Analysis
by VulDB Data Team • 10/15/2026
The reported server-side request forgery (SSRF) vulnerability within Synology's Download Station application represents a significant security risk for environments where the service is exposed to network traffic, particularly when authentication controls are insufficient or compromised. SSRF vulnerabilities occur when an application fetches a remote resource without validating the user-supplied URL, allowing an attacker to force the server to make requests to internal or external destinations that would otherwise be inaccessible. In this specific instance, the flaw resides in how Download Station processes URLs provided by authenticated users during download operations. If a remote attacker successfully obtains valid credentials for a user account on the target system, they can manipulate these URL parameters to direct the server's HTTP client toward sensitive internal resources or local services that are not intended to be publicly accessible.
The operational impact of this vulnerability is primarily centered around unauthorized data exfiltration and potential reconnaissance within the internal network architecture. By exploiting the SSRF flaw, an attacker with a valid user account can cause the Download Station service to retrieve content from localhost interfaces, internal API endpoints, or other services running on the same host that typically lack authentication mechanisms. This capability allows the attacker to read application data, configuration files, and potentially sensitive information stored within the NAS environment. The severity of this impact is amplified by the fact that it requires only a standard user account rather than administrative privileges, lowering the barrier for exploitation while still enabling access to critical system resources.
From a technical classification perspective, this vulnerability aligns with CWE-918, which defines Server-Side Request Forgery (SSRF). The flaw indicates an insufficient validation of input data before it is processed by server-side functions that initiate network connections. Furthermore, in the context of the MITRE ATT&CK framework, this behavior corresponds to techniques involving internal network discovery and credential access through service exploitation. Attackers can leverage SSRF as a pivot point to map out the internal network topology or extract credentials stored in local configuration files, thereby escalating their position within the compromised environment. The lack of strict allow-listing for destination hosts is the root cause, enabling requests to loopback addresses such as 127.0.0.1 or ::1, which often host administrative interfaces and database services without additional authentication layers.
To mitigate this vulnerability, organizations must ensure that all instances of Download Station are updated to version 5.10.1.312 or later for the 5.10 branch, or version 5.11.2.321 and later for the 5.11 branch. These versions contain patches that implement stricter validation logic for URL inputs, preventing the server from initiating connections to unauthorized internal addresses. In addition to applying these software updates, administrators should enforce strong password policies and multi-factor authentication where possible to reduce the risk of credential compromise. Network segmentation strategies can also provide an additional layer of defense by isolating critical services behind firewalls that restrict inbound traffic even if SSRF is attempted, ensuring that loopback interfaces remain inaccessible from application-level processes unless explicitly required for legitimate functionality.