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EUVD-2026-280153

fkie_cve-2026-34715

ewe is a Gleam web server. Prior to version 3.0.6, the encode_headers function in src/ewe/internal/encoder.gleam directly interpolates response header keys and values into raw HTTP bytes without validating or stripping CRLF (\r\n) sequences. An application that passes user-controlled data into response headers (e.g., setting a Location redirect header from a request parameter) allows an attacker to inject arbitrary HTTP response content, leading to response splitting, cache poisoning, and possible cross-site scripting. Notably, ewe does validate CRLF in incoming request headers via validate_field_value() in the HTTP/1.1 parser — but provides no equivalent protection for outgoing response headers in the encoder. This issue has been patched in version 3.0.6.

GHSA-x2w3-23jr-hrpf — ewe Has Improper Neutralization of CRLF Sequences in HTTP Headers (HTTP Request/Response Splitting)

Affected: Hex: ewe

### Summary

The `encode_headers` function in `src/ewe/internal/encoder.gleam` directly interpolates response header keys and values into raw HTTP bytes without validating or stripping CRLF (`\r\n`) sequences. An application that passes user-controlled data into response headers (e.g., setting a `Location` redirect header from a request parameter) allows an attacker to inject arbitrary HTTP response content, leading to response splitting, cache poisoning, and possible cross-site scripting.

Notably, ewe *does* validate CRLF in **incoming** request headers via `validate_field_value()` in the HTTP/1.1 parser — but provides no equivalent protection for **outgoing** response headers in the encoder.

### Details

**File:** `src/ewe/internal/encoder.gleam`

**Vulnerable code:** ```gleam fn encode_headers(headers: List(#(String, String))) -> BitArray { let headers = list.fold(headers, <<>>, fn(acc, headers) { let #(key, value) = headers <<acc:bits, key:utf8, ": ", value:utf8, "\r\n">> })

<<headers:bits, "\r\n">> } ```

Both `key` and `value` are embedded directly into the `BitArray` output. If either contains `\r\n`, the resulting bytes become a structurally valid but attacker-controlled HTTP response, terminating the current header early and injecting new headers or a second HTTP response.

**Contrast with request parsing** (`src/ewe/internal/http1.gleam`): incoming header values are protected: ```gleam use value <- try( validate_field_value(value) |> re…