CVE-2026-34715: ewe Has Improper Neutralization of CRLF Sequences in HTTP Headers (HTTP Request/Response Splitting)

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-02 · updated 2026-07-24
Weakness: CWE-113

Description

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.

Affected products

vshakitskiy ewe: before 3.0.6 — fixed in 3.0.6

How to fix

Upgrade to a fixed version: vshakitskiy ewe 3.0.6. Check the vendor advisory for mitigations.

References

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