Highly exploitable, CVE-2026-56661 poses a critical security risk that could lead to severe breaches.
Status: Deferred
Published on: 01 Oct 2026, 20:17 UTC
CVSS Release: version 3
security-advisories@github.com
Secondary
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:L/A:L
CVE-2026-56661: GetSimple CMS is a content management system (CMS), and GetSimple CMS CE is the community edition of that CMS. Prior to version 1.5, the update handler fetches a user-supplied URL with file_get_contents() after only format validation (FILTER_VALIDATE_URL) — there is no validation of the request destination. An attacker who can submit the form can make the server issue requests to arbitrary destinations, including internal-only services and cloud metadata endpoints (169.254.169.254). The fetched response body is written to a web-accessible file (/Tmpfile.zip) and is not deleted when the content is not a valid ZIP, turning this into a full-read SSRF: the attacker can retrieve the response of the internal request directly. This issue has been patched in version 1.5.
The exploitability of CVE-2026-56661 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
The exploitability of CVE-2026-56661 is influenced by multiple factors. Security teams should analyze system configurations and apply appropriate countermeasures to mitigate threats.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-56661, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-56661, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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