Weakness Type (CWE)

CWE-93 — CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')

CAPEC

CVSS 4.0 Score

6.9

MEDIUM

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:H/SA:N

Vulnerability description

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in benoitc hackney allows HTTP Request/Response Splitting.

The WebSocket upgrade code in src/hackney_ws.erl copies the host, path, headers (ExtraHeaders), and protocols options from the caller-supplied opts map into the internal #ws_data{} record in init/1 and then splices them verbatim into the raw HTTP/1.1 upgrade request by binary concatenation in do_handshake/1. No CRLF or NUL stripping is performed at any of these four injection sites. An attacker who controls any of these options — for example by forwarding URL components or header values from untrusted input into hackney_ws:start_link/1 — can inject arbitrary HTTP headers into the outbound WebSocket upgrade request, leading to header injection, credential spoofing toward the upstream server, log and cache poisoning, or request smuggling via intermediary proxies.

This issue affects hackney: from 2.0.0 before 4.0.1.

Affected

pkg:hex/hackney

Module Source File Routine
hackney_ws src/hackney_ws.erl hackney_ws:do_handshake/1
hackney_ws:init/1
Status Type Version Changes / Fixed in
affected semver ⓘ 2.0.0 < 4.0.1

pkg:github/benoitc/hackney

Module Source File Routine
hackney_ws src/hackney_ws.erl hackney_ws:do_handshake/1
hackney_ws:init/1
Status Type Version Changes / Fixed in
affected git ⓘ 690cecaf23 < 52310ca807

References

Credits

  • Finder: Peter Ullrich
  • Remediation developer: Benoit Chesneau
  • Analyst: Jonatan Männchen

CVE record as JSON:  GET /cves/CVE-2026-47072.json
OSV record as JSON:  GET /osv/EEF-CVE-2026-47072.json