---
id: CVE-2026-112880
title: >-
  CRLF injection in Proxy-Authorization header built from proxy_auth_fun in
  hackney
summary: >-
  Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP
  Request/Response Splitting') vulnerability in hackney_http_connect in benoitc
  hackney allows HTTP Request Splitting via the value a proxy_auth_fun callback
  returns. After a…
severity: low
cvss: 2.1
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-113
vendor: benoitc
product: hackney
affected:
  - hackney >= 2.0.0 < 4.9.0
  - >-
    benoitc/hackney >= 5df5a74a2817d5b12880d217db33253ff1fae1b5 <
    5ee7d7d19eba27e774667d472feb1e93a08af7f9
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-26T15:00:47.038622Z'
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T15:35:50.632Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112880'
references:
  - url: 'https://github.com/benoitc/hackney/releases/tag/4.9.0'
    label: hackney 4.9.0 release notes
  - url: 'https://cna.erlef.org/cves/CVE-2026-112880.html'
    label: EEF CNA record for CVE-2026-112880
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-112880'
    label: OSV record EEF-CVE-2026-112880
  - url: 'https://github.com/benoitc/hackney/pull/989'
    label: Refuse CR/LF/NUL in the proxy_auth_fun result (benoitc/hackney#989)
  - url: >-
      https://github.com/benoitc/hackney/commit/5df5a74a2817d5b12880d217db33253ff1fae1b5
    label: Introducing commit 5df5a74 in benoitc/hackney
  - url: >-
      https://github.com/benoitc/hackney/commit/5ee7d7d19eba27e774667d472feb1e93a08af7f9
    label: Fix commit 5ee7d7d in benoitc/hackney
tags:
  - cve.org
ingestedAt: '2026-10-26T14:27:31.816Z'
---

## Overview

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in hackney_http_connect in benoitc hackney allows HTTP Request Splitting via the value a proxy_auth_fun callback returns. After a 407 response from an HTTP CONNECT proxy, hackney_http_connect:handle_proxy_auth/11 calls the caller's proxy_auth_fun with the status code and the response headers and writes the returned binary into the Proxy-Authorization line of the CONNECT retry without checking it. A CR, LF or NUL byte in that value adds header lines to the request sent to the proxy.

The value is attacker-influenced when the callback derives it from untrusted data, for example from the proxy's challenge headers. Other caller-supplied values on the CONNECT path, such as the target host and the request headers, were already checked for control bytes.

This issue affects hackney: from 2.0.0 before 4.9.0.

## Affected

- `hackney >= 2.0.0 < 4.9.0`
- `benoitc/hackney >= 5df5a74a2817d5b12880d217db33253ff1fae1b5 < 5ee7d7d19eba27e774667d472feb1e93a08af7f9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

Check the value your proxy_auth_fun is about to return for CR, LF and NUL bytes and return {error, Reason} instead when one is present. The callback runs in the application, so the check can be made there.