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

Status: published. Published: 2026-06-10. Updated: 2026-11-11.

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 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to inets from 5.10.4 before 7.0, and ftp from 1.0 before 1.2.3.1, 1.2.4.1, and 1.2.6.

## Remediation

- workaround: Pass {ftp_extension, true} to ftp:open/2 to use EPSV instead of PASV. Alternatively, pass {mode, active} to use active mode, or pass {ipfamily, inet6} to force IPv6, both of which bypass the vulnerable PASV path. (source: CNA: EEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/521bcfa24407ee8cb5614823cf905c37ea3aa605
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/2691a806231ffd0490a8a9e20500dec0c7e73727

## Affected products and versions

- Erlang / OTP (otp): ≥ 17.4; < * (affected, otp); unaffected at 27.3.4.13; unaffected at 28.5.0.2; unaffected at 29.0.2. Source: CNA: EEF
- Erlang / OTP (inets): ≥ 5.10.4; < 7.0 (affected, otp). Source: CNA: EEF
- Erlang / OTP (ftp): ≥ 1.0; < * (affected, otp); unaffected at 1.2.3.1; unaffected at 1.2.4.1; unaffected at 1.2.6. Source: CNA: EEF
- Erlang / OTP (erlang/otp): ≥ be95772ee1fcfe71045ef070130bea7a910b81e3; < * (affected, git); unaffected at 521bcfa24407ee8cb5614823cf905c37ea3aa605; unaffected at 2691a806231ffd0490a8a9e20500dec0c7e73727. Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N; source: CNA: EEF

- CISA KEV: No listing in collected sources

- EPSS: 0.23% as of 2026-11-10; percentile 14.47%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-918

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/erlang/otp/security/advisories/GHSA-24cv-hwgr-37fq (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-48858.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-48858 (CNA: EEF; related)

- https://www.erlang.org/doc/system/versions.html#order-of-versions (CNA: EEF; x_version-scheme)

- https://github.com/erlang/otp/commit/be95772ee1fcfe71045ef070130bea7a910b81e3 (CNA: EEF; related)

- https://github.com/erlang/otp/commit/521bcfa24407ee8cb5614823cf905c37ea3aa605 (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/2691a806231ffd0490a8a9e20500dec0c7e73727 (CNA: EEF; patch)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-48858; retrieved 2026-11-11; source updated 2026-11-11

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-48858; retrieved 2026-11-11; source updated Not reported

Revision: 248f8787c7b68582785fd0523231ae53c4e60f74438cbb935b28d386932f4863

Canonical: https://y2.dev/cve/CVE-2026-48858

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