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CVE-2015-3306ProFTPD Improper Access Control Vulnerability

Patch nowCritical10.0Exploited, CISA due date 2026-10-11EPSS 99%, higher than 100% of scored CVEs

CVE-2015-3306 is a improper access control in ProFTPD, rated critical (10.0 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published · Updated · NVD status: Analyzed

What it is

Access to a resource or action is not restricted to the people meant to have it.

How it is reached

An attacker can exploit it over the network, without an account, and nobody has to click anything.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker reach data or actions their role should not allow. The damage can spread past the vulnerable component into others.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-08: it is being exploited in the wild. It can be exploited automatically, at scale. EPSS estimates a 99% chance of exploitation activity in the next 30 days, higher than 100% of scored CVEs.

What to do

  1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2026-10-11.
  2. No fixed version is listed yet. Find every place ProFTPD runs, watch the references for a fix, and plan a replacement if it is no longer supported.
  3. While there is no fix, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
  4. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

The mod_copy module in ProFTPD 1.3.5 allows remote attackers to read and write to arbitrary files via the site cpfr and site cpto commands.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
  • Permission checks in APIs and admin surfaces. The flaw sits between one role or tenant and another.
  • Multi-tenant services. The flaw sits between one role or tenant and another.

Trust boundaries in play

  • Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
  • Isolation between components. The impact crosses out of the vulnerable component into others it should be isolated from.
  • Between one role or tenant and another. An attacker who crosses it can reach data or actions their role should not allow.

Questions to answer about your own systems

  • Where does ProFTPD run in your systems, and at which version?
  • Which of those instances can be reached from the internet or partner networks?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

Read more

Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.