CVE-2026-47072: hackney — Exploit & Fix

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0048

Probability of exploitation

0.38%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-93 CWE-93

Affected Products

Vendor	Product	Versions
benoitc	hackney	2.0.0 — 4.0.1

References

Advisories & Patches

https://cna.erlef.org/cves/CVE-2026-47072.html https://github.com/benoitc/hackney/commit/52310ca807e7b48441ba0e9129171f535313fdd1 https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fg https://osv.dev/vulnerability/EEF-CVE-2026-47072 https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fg

Exploits

https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fg https://github.com/benoitc/hackney/security/advisories/GHSA-f9vr-g2g2-x9fg

Frequently Asked Questions

What is CVE-2026-47072? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-47072? +

CVE-2026-47072 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0048, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-47072? +

CVE-2026-47072 affects products from benoitc, specifically: hackney. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-47072? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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