Monsta FTP before 2.14.5 contains a server-side request forgery vulnerability in the fetchRemoteFile action caused by an incomplete IP blocklist check in the isBlockedIP() function, which fails to detect embedded IPv4 addresses within IPv4-mapped IPv6 addresses. An unauthenticated attacker can obtain a CSRF token from the public getSystemVars endpoint and submit a fetchRemoteFile request with a source URL resolving to an IPv4-mapped address, causing the server to issue HTTP requests to internal services and write responses to an attacker-controlled FTP destination, enabling retrieval of cloud instance metadata credentials.
https://www.vulncheck.com/advisories/monsta-ftp-ssrf-via-ipv4-mapped-ipv6-address-bypass
Published: 2026-07-08
Updated: 2026-07-08
Base Score: 7.8
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:N/A:N
Severity: High
Base Score: 8.6
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Severity: High
Base Score: 7.7
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N
Severity: High