6.5Medium

Haxx Curl

CVE-2026-3784

curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection.

What this means for your business

  • It affects Haxx Curl. It matters if your company, or a supplier that handles your data, runs it.
  • Code showing how to exploit it has been published, but real attacks have not been confirmed.
  • An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 0.4% chance of attack attempts being seen in the next 30 days, ranking above 34% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Haxx Curl, and which version. The affected versions are listed further down this page.
  2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Scoring

CVSS
6.5 (v3.1)
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-305
Assigned by
2499f714-1537-4658-8207-48ae4bb9eae9

Dates

Published
2026-03-11
Last modified
2026-09-15
Sources
NVD

Affected products

  • Haxx Curl7.7 - 8.18.0

As listed in the NVD configuration data. Not a statement about your estate.

References