5.9Medium
Haxx Curl
CVE-2026-4873
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.
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 0.3% chance of attack attempts being seen in the next 30 days, ranking above 26% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Haxx Curl, and which version. The affected versions are listed further down this page.
- 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
- 5.9 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N- Weakness
- CWE-319
- Assigned by
- 2499f714-1537-4658-8207-48ae4bb9eae9
Dates
- Published
- 2026-05-13
- Last modified
- 2026-09-15
- Sources
- NVD
Affected products
- Haxx Curl7.20.0 - 8.20.0
As listed in the NVD configuration data. Not a statement about your estate.