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CVE-2026-47072

28
FAUCET Score

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.

First published: May 25, 2026Last modified: May 25, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.0.0, < 4.0.1CPE matchmatch criteria
cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

6.9MEDIUM

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
LOW
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
HIGH
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.54%
Probability of exploitation in next 30 days
EPSS Percentile
42.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0054 is in the 20th percentile among its peer group of 51,553 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

erlangpatch availablevia ghsa
Product: hackneyFixed in: 4.0.1
github_advisorypatch availablevia nvd_reference
View patch

Vendor Advisories (1)

erlangGHSA-f9vr-g2g2-x9fgmedium

Hackney has CRLF / header injection in WebSocket upgrade request

Jun 26, 2026

References

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