Summary
elFinder: CSRF in netmount allows forced FTP mounts and server-side FTP connections
Impact
An attacker who can cause a victim browser to request the connector can bypass the intended CSRF protection for netmount. In the shipped minimal connector configuration, this lets the attacker:
- force the victim's elFinder session to persist an attacker-chosen FTP network volume;
- cause the PHP server to initiate an outbound FTP connection to an attacker-chosen host and port;
- send attacker-supplied FTP username/password values to that endpoint; and
- expose the victim's later file-manager UI to the mounted remote volume.
The proof demonstrates a security boundary mismatch: the same connector rejects another mutating command without the CSRF header but accepts netmount without it. The observed server-side FTP command sequence confirms that the request reaches the network sink, not just a harmless JSON code path.
The impact is bounded by deployment and browser behavior. In a deployment with no surrounding authentication, direct callers may be able to use the connector normally; in the common authenticated-file-manager deployment model, the missing netmount CSRF check lets a cross-site attacker perform this state-changing/server-side network action in the victim's authenticated session.
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
CVE-2026-81890 has a CVSS score of 5.4 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.1.70); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-81890? CVE-2026-81890 is a medium-severity cross-site request forgery (CSRF) vulnerability in studio-42/elfinder (composer), affecting versions < 2.1.70. It is fixed in 2.1.70. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- How severe is CVE-2026-81890? CVE-2026-81890 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of studio-42/elfinder are affected by CVE-2026-81890? studio-42/elfinder (composer) versions < 2.1.70 is affected.
- Is there a fix for CVE-2026-81890? Yes. CVE-2026-81890 is fixed in 2.1.70. Upgrade to this version or later.
- Is CVE-2026-81890 exploitable, and should I be worried? Whether CVE-2026-81890 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-81890 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-81890? Upgrade
studio-42/elfinderto 2.1.70 or later.