VulnerabilityAnalyzed

CVE-2026-47072

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

MEDIUM 6.9EPSS 0.54%

Does this matter?

Lower severity and a low EPSS score (0.54%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 4.0: 6.9 MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.54% probability · 44th percentile
CISA KEV: Not listed
Weakness: CWE-93
Affected: benoitc/hackney
Source: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

References

https://cna.erlef.org/cves/CVE-2026-47072.htmlPatch, Third Party Advisory
https://github.com/benoitc/hackney/commit/52310ca807e7b48441ba0e9129171f535313fdd1Patch
https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fgExploit, Patch, Vendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-47072Patch, Third Party Advisory
https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fgExploit, Patch, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.