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EUVD-2026-276770

2026-10-07T14:29:42.809170+00:00

EUVD-2026-276770

fkie_cve-2026-32881

2026-10-07T14:29:42.809223+00:00

ewe is a Gleam web server. ewe is a Gleam web server. Versions 0.6.0 through 3.0.4 are vulnerable to authentication bypass or spoofed proxy-trust headers. Chunked transfer encoding trailer handling merges declared trailer fields into req.headers after body parsing, but the denylist only blocks 9 header names. A malicious client can exploit this by declaring these headers in the Trailer field and appending them after the final chunk, causing request.set_header to overwrite legitimate values (e.g., those set by a reverse proxy). This enables attackers to forge authentication credentials, hijack sessions, bypass IP-based rate limiting, or spoof proxy-trust headers in any downstream middleware that reads headers after ewe.read_body is called. This issue has been fixed in version 3.0.5.

GHSA-9w88-79f8-m3vp — Permissive List of Allowed Inputs in ewe

2026-10-07T14:29:42.809287+00:00

Affected: Hex: ewe

## Summary

ewe's chunked transfer encoding trailer handling merges declared trailer fields into `req.headers` after body parsing, but the denylist only blocks 9 header names. Security-sensitive headers like `authorization`, `cookie`, and `x-forwarded-for` can be injected or overwritten by a malicious client via trailers, potentially bypassing authentication or spoofing proxy-trust headers.

## Impact

When `ewe.read_body` processes a chunked request with a `Trailer` header, it calls `handle_trailers` (`ewe/internal/http1.gleam:493`), which merges declared trailer fields into `req.headers` via `request.set_header` (line 517). The `is_forbidden_trailer` denylist (line 534) only blocks 9 header names: `transfer-encoding`, `content-length`, `host`, `cache-control`, `expect`, `max-forwards`, `pragma`, `range`, and `te`.

Security-sensitive headers are not blocked, including:

- `authorization` — attacker can inject or overwrite Bearer tokens - `cookie` / `set-cookie` — attacker can inject session cookies - `proxy-authorization` — attacker can inject proxy credentials - `x-forwarded-for`, `x-forwarded-host`, `x-forwarded-proto` — attacker can spoof proxy-trust headers - `x-real-ip` — attacker can spoof client IP

A malicious client can inject these headers by declaring them in the `Trailer` request header and including them after the final `0\r\n` chunk. If the header already exists (e.g., set by a reverse proxy), `request.set_header` overwrites it. Any application logic that rea…