---
id: CVE-2023-27535
title: >-
  An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP
  connection reuse feature that can result in wrong credentials being used
  during subsequent transfers
summary: >-
  An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP
  connection reuse feature that can result in wrong credentials being used
  during subsequent transfers. Previously created connections are kept in a
  connection pool…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-305
  - CWE-287
vendor: haxx
product: libcurl
affected:
  - 'libcurl >= 7.13.0, <= 7.88.1'
  - fedora = 36
  - debian_linux = 10.0
  - active_iq_unified_manager
  - ontap_9
  - h300s_firmware
  - h500s_firmware
  - h700s_firmware
  - h410s_firmware
  - 'universal_forwarder >= 8.2.0, < 8.2.12'
  - 'universal_forwarder >= 9.0.0, < 9.0.6'
  - universal_forwarder = 9.1.0
patched:
  - universal_forwarder 9.0.6
published: '2023-03-30'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T23:17:16.450'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-27535'
references:
  - url: 'https://hackerone.com/reports/1892780'
    label: support@hackerone.com
  - url: 'https://lists.debian.org/debian-lts-announce/2023/04/msg00025.html'
    label: support@hackerone.com
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/36NBD5YLJXXEDZLDGNFCERWRYJQ6LAQW/
    label: support@hackerone.com
  - url: 'https://security.gentoo.org/glsa/202310-12'
    label: support@hackerone.com
  - url: 'https://security.netapp.com/advisory/ntap-20230420-0010/'
    label: support@hackerone.com
  - url: 'https://hackerone.com/reports/1892780'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2023/04/msg00025.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/36NBD5YLJXXEDZLDGNFCERWRYJQ6LAQW/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.gentoo.org/glsa/202310-12'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20230420-0010/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-806742.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-943925.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.01607
epssPercentile: 0.75405
ingestedAt: '2026-10-15T00:02:07.130Z'
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-06-03T18:24:11.710118Z'
---

## Overview

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

## Affected

- `libcurl >= 7.13.0, <= 7.88.1`
- `fedora = 36`
- `debian_linux = 10.0`
- `active_iq_unified_manager`
- `ontap_9`
- `h300s_firmware`
- `h500s_firmware`
- `h700s_firmware`
- `h410s_firmware`
- `universal_forwarder >= 8.2.0, < 8.2.12`
- `universal_forwarder >= 9.0.0, < 9.0.6`
- `universal_forwarder = 9.1.0`

## Remediation

Upgrade past the affected range:

- `universal_forwarder 9.0.6`