CVE-2026-79670 in Ech0
Summary
by MITRE • 08/25/2026
Ech0 before 4.4.3 contains a stored cross-site scripting vulnerability in the file upload endpoint that validates Content-Type using only client-supplied headers without server-side inspection. Attackers with admin privileges can upload SVG or HTML files containing JavaScript that executes in the application origin when accessed by any user, enabling session hijacking and data exfiltration.
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Analysis
by VulDB Data Team • 08/25/2026
The vulnerability identified in Ech0 versions prior to 4.4.3 represents a critical security flaw rooted in improper input validation within the file upload mechanism. Specifically, the system relies exclusively on client-supplied Content-Type headers to determine whether an uploaded file is safe for processing or storage. This approach fundamentally violates the principle of trusting only server-side data, as HTTP headers are easily spoofed by any entity capable of crafting custom requests. By failing to perform server-side inspection of the actual file content using magic numbers or MIME type detection libraries, the application allows malicious actors to bypass security controls designed to restrict executable or script-based file types. This misconfiguration creates a direct pathway for attackers to inject hostile code into the application environment through legitimate administrative interfaces that permit file uploads.
The technical exploitation of this flaw involves an attacker with existing administrator privileges uploading files such as SVG images or HTML documents embedded with malicious JavaScript payloads. Because the server accepts these files based on falsified headers rather than verifying their true nature, they are stored and subsequently served to other users without sanitization. When a victim user accesses a page that renders or previews this uploaded content, the browser interprets the embedded script as part of the application's origin. This results in a Stored Cross-Site Scripting scenario where the malicious code executes within the context of the trusted domain, granting it full access to cookies, session tokens, and local storage associated with Ech0.
The operational impact of this vulnerability is severe due to its potential for widespread compromise once triggered. Since the script persists on the server side, every user who views the affected content becomes a target, facilitating mass account takeover attacks without requiring further interaction from the attacker beyond the initial upload. The primary consequences include session hijacking, where attackers can impersonate legitimate users and administrators, leading to unauthorized access to sensitive data and system configurations. Additionally, the ability to execute arbitrary JavaScript enables comprehensive data exfiltration, allowing adversaries to steal confidential information stored within the application interface or redirect victims to phishing sites designed to capture additional credentials. This level of compromise undermines the integrity and confidentiality guarantees provided by the Ech0 platform.
To mitigate this risk, immediate remediation requires upgrading Ech0 to version 4.4.3 or later where these validation checks have been corrected. In addition to software updates, organizations should implement strict server-side file type verification using robust libraries that inspect file signatures rather than relying on HTTP headers. It is also advisable to enforce Content Security Policy directives that restrict the execution of inline scripts and limit script sources to trusted domains only. Furthermore, applying output encoding when rendering user-supplied content in HTML contexts can provide a defense-in-depth layer against any residual scripting risks. Regular security audits focusing on file upload endpoints are recommended to ensure compliance with industry standards such as CWE-94 for improper control of generation of code and CWE-20 for improper input validation, aligning defensive measures with established best practices outlined by the MITRE ATT&CK framework under techniques related to client-side injection.