Echo: X-Real-IP extractor trusts the header value instead of the sending peer

Echo is a Go web framework. From 5.0.0 until 5.4.1, Echo v5's ExtractIPFromRealIPHeader validates whether the client-supplied X-Real-IP value belongs to a trusted range instead of validating the direct network peer. A client reaching Echo directly, or through a proxy that preserves the header, can supply a loopback or private address and have Context.RealIP return that spoofed identity. Applications using the extractor for IP allowlists, rate limiting, audit logs, or forwarding headers can consequently trust an attacker-controlled address; the default direct extractor and Echo v4 are unaffected. This issue is fixed in 5.4.1.

Source published

28 Oct 2026 19:03:56 UTC

Source modified

29 Oct 2026 20:54:10 UTC

Observed here

29 Oct 2026 21:48:56 UTC

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CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N