CVE-2026-48858: ftp client PASV response IP not validated against control peer, enabling SSRF and FTP bounce attacks

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-10 · updated 2026-10-25
Weakness: CWE-918

Description

Server-Side Request Forgery (SSRF) vulnerability in Erlang/OTP ftp (ftp_internal module) allows FTP bounce attacks and SSRF via an unvalidated PASV response IP address. The ftp_internal:handle_ctrl_result/2 PASV handler (mode=passive, ipfamily=inet, ftp_extension=false) extracts the IP address from the server's 227 response and passes it directly to gen_tcp:connect/4 without validating it against the control connection peer address. The adjacent EPSV handlers correctly call peername(CSock) to derive the IP from the control connection, but the PASV handler does not. A malicious or compromised FTP server can redirect the client's data connection to an arbitrary internal host and port. On read operations (ftp:ls/1,2, ftp:nlist/1,2, ftp:recv/2,3), data from the redirected target is returned to the caller. On write operations (ftp:send/2,3, ftp:append/2,3), file content is sent to the redirected target. This enables SSRF against internal hosts, cloud metadata endpoints, and FTP bounce attacks against third-party hosts. The vulnerable path is the default configuration (mode=passive, ipfamily=inet, ftp_extension=false). RFC 2577 section 3 explicitly recommends validating the PASV response IP against the control connection peer. The ftp application is deprecated and scheduled for removal in OTP-30. This vulnerability is associated with program files lib/inets/src/ftp/ftp_internal.erl (inets 5.10.4 through 6.5, OTP 17.4 through 20.3) and lib/ftp/src/ftp_internal.erl (ftp 1.0 and later, OTP 21.0 and later). This issue affects OTP from OTP 17.4 before OTP 29.0.2, OTP 28.5.0.2 and OTP 27.3.4.13, corresponding to inets from 5.10.4 before 7.0 and ftp from 1.0 before 1.2.6, 1.2.4.1 and 1.2.3.1.

Affected products

Erlang/Inets: from 5.10.4 before 7.0 — fixed in 7.0
Erlang OTP: from 17.4 before 27.3.4.13; from 28.0 before 28.5.0.2; from 29.0 before 29.0.2 — fixed in 27.3.4.13, 28.5.0.2, 29.0.2
Erlang Ftp: from 1.0 before 1.2.3.1; from 1.2.4 before 1.2.4.1; from 1.2.5 before 1.2.6 — fixed in 1.2.3.1, 1.2.4.1, 1.2.6

How to fix

Upgrade to a fixed version: Erlang/Inets 7.0; Erlang OTP 27.3.4.13, 28.5.0.2, 29.0.2; Erlang Ftp 1.2.3.1, 1.2.4.1, 1.2.6. Check the vendor advisory for mitigations.

References

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