---
id: CVE-2023-27538
title: >-
  An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where
  it reuses a previously established SSH connection despite the fact that an SSH
  option was modified, which should have prevented reuse
summary: >-
  An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where
  it reuses a previously established SSH connection despite the fact that an SSH
  option was modified, which should have prevented reuse. libcurl maintains a
  poo…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-305
  - CWE-287
vendor: haxx
product: libcurl
affected:
  - 'libcurl >= 7.16.1, < 8.0.0'
  - fedora = 36
  - debian_linux = 10.0
  - active_iq_unified_manager
  - clustered_data_ontap = 9.0
  - brocade_fabric_operating_system_firmware
  - 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:
  - libcurl 8.0.0
  - universal_forwarder 9.0.6
published: '2023-03-30'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T23:17:16.973'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-27538'
references:
  - url: 'https://hackerone.com/reports/1898475'
    label: support@hackerone.com
  - url: 'https://lists.debian.org/debian-lts-announce/2023/04/msg00025.html'
    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/1898475'
    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://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-077170.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - 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-943925.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
epss: 0.01246
epssPercentile: 0.68727
ingestedAt: '2026-10-15T00:02:07.131Z'
---

## Overview

An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where it reuses a previously established SSH connection despite the fact that an SSH option was modified, which should have prevented reuse. libcurl maintains a pool of previously used connections to reuse them for subsequent transfers if the configurations match. However, two SSH settings were omitted from the configuration check, allowing them to match easily, potentially leading to the reuse of an inappropriate connection.

## Affected

- `libcurl >= 7.16.1, < 8.0.0`
- `fedora = 36`
- `debian_linux = 10.0`
- `active_iq_unified_manager`
- `clustered_data_ontap = 9.0`
- `brocade_fabric_operating_system_firmware`
- `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:

- `libcurl 8.0.0`
- `universal_forwarder 9.0.6`