---
id: CVE-2023-27533
title: >-
  A vulnerability in input validation exists in curl <8.0 during communication
  using the TELNET protocol may allow an attacker to pass on maliciously crafted
  user name and "telnet options" during server negotiation
summary: >-
  A vulnerability in input validation exists in curl <8.0 during communication
  using the TELNET protocol may allow an attacker to pass on maliciously crafted
  user name and "telnet options" during server negotiation. The lack of proper
  inpu…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'
cwe:
  - CWE-75
  - CWE-74
vendor: haxx
product: curl
affected:
  - 'curl >= 7.0.0, <= 7.881'
  - fedora = 36
  - active_iq_unified_manager
  - clustered_data_ontap = 9.0
  - 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: '2026-10-14T23:17:16.033'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-27533'
references:
  - url: 'https://hackerone.com/reports/1891474'
    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-20230420-0011/'
    label: support@hackerone.com
  - url: 'https://hackerone.com/reports/1891474'
    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-20230420-0011/'
    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-943925.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.01993
epssPercentile: 0.80283
ingestedAt: '2026-10-15T00:02:07.129Z'
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-02-13T20:09:15.311824Z'
scores:
  nvd: 8.8
  adp: 9.8
---

## Overview

A vulnerability in input validation exists in curl <8.0 during communication using the TELNET protocol may allow an attacker to pass on maliciously crafted user name and "telnet options" during server negotiation. The lack of proper input scrubbing allows an attacker to send content or perform option negotiation without the application's intent. This vulnerability could be exploited if an application allows user input, thereby enabling attackers to execute arbitrary code on the system.

## Affected

- `curl >= 7.0.0, <= 7.881`
- `fedora = 36`
- `active_iq_unified_manager`
- `clustered_data_ontap = 9.0`
- `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`