CRLF injection in cookie domain/path options in hackney

Weakness Type (CWE)

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

CAPEC

CAPEC-34 — CAPEC-34 HTTP Response Splitting

CVSS 4.0 Score

2.1

LOW

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

Vulnerability description

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

The hackney_cookie:setcookie/3 function in src/hackney_cookie.erl validates the Name and Value arguments against CRLF and control characters, but concatenates the domain and path options verbatim into the output iolist with no equivalent check. An attacker who controls either option — for example by supplying a Host header value forwarded as the cookie domain, or a request path forwarded as the cookie path — can inject a literal CRLF sequence and arbitrary additional Set-Cookie headers into the HTTP response.

This issue affects hackney: from 0.9.0 before 4.0.1.

Affected

`pkg:hex/hackney`

Module	Source File	Routine
`hackney_cookie`	`src/hackney_cookie.erl`	`hackney_cookie:setcookie/3`

Status	Type	Version	Changes / Fixed in
affected	semver ^ⓘ	`0.9.0`	< `4.0.1`

`pkg:github/benoitc/hackney`

Module	Source File	Routine
`hackney_cookie`	`src/hackney_cookie.erl`	`hackney_cookie:setcookie/3`

Status	Type	Version	Changes / Fixed in
affected	git ^ⓘ	`602d5c7f2e`	< `8e02b99c28`

References

https://github.com/benoitc/hackney/security/advisories/GHSA-mp55-p8c9-rfw2 vendor-advisory related
https://osv.dev/vulnerability/EEF-CVE-2026-47069 related
https://github.com/benoitc/hackney/commit/8e02b99c28aea1b3fa2ddc0e66f51fe5bb0ac540 patch

Credits

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

CVE record as JSON: GET /cves/CVE-2026-47069.json
OSV record as JSON: GET /osv/EEF-CVE-2026-47069.json