---
id: CVE-2026-4873
title: |-
  A vulnerability exists where a connection requiring TLS incorrectly reuses an
  existing unencrypted connection from the same connection pool
summary: |-
  A vulnerability exists where a connection requiring TLS incorrectly reuses an
  existing unencrypted connection from the same connection pool. If an initial
  transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request
  to …
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-319
  - CWE-295
vendor: haxx
product: curl
affected:
  - 'curl >= 7.20.0, < 8.20.0'
patched:
  - curl 8.20.0
published: '2026-05-13'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:28.367'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-4873'
references:
  - url: 'https://curl.se/docs/CVE-2026-4873.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-4873.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3621851'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'http://www.openwall.com/lists/oss-security/2026/04/29/7'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-05-13T19:29:14.521822Z'
epss: 0.00359
epssPercentile: 0.26987
ingestedAt: '2026-09-15T07:33:29.264Z'
---

## Overview

A vulnerability exists where a connection requiring TLS incorrectly reuses an
existing unencrypted connection from the same connection pool. If an initial
transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request
to that same host bypasses the TLS requirement and instead transmit data
unencrypted.

## Affected

- `curl >= 7.20.0, < 8.20.0`

## Remediation

Upgrade past the affected range:

- `curl 8.20.0`