What is CVE-2026-3784?

CVE-2026-3784 is a medium-severity vulnerability in Curl, classified under Authentication Bypass by Primary Weakness. CVSS score: 6.5/10. Published 2026-03-11.

How severe is CVE-2026-3784?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in 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.

Published 2026-03-11 · last modified 2026-09-15.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (36.7th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 36.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.000

Affected products

Curl — versions 8.18.0, 8.17.0, 8.16.0
Haxx Curl

Weakness classification (CWE)

CWE-305 — Authentication Bypass by Primary Weakness

References

2499f714-1537-4658-8207-48ae4bb9eae9 (Vendor Advisory)
2499f714-1537-4658-8207-48ae4bb9eae9 (Patch, Vendor Advisory)
2499f714-1537-4658-8207-48ae4bb9eae9 (Exploit, Third Party Advisory, Issue Tracking)
af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)
0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

Frequently asked questions

What is CVE-2026-3784?: CVE-2026-3784 is a medium-severity vulnerability in Curl, classified under Authentication Bypass by Primary Weakness. CVSS score: 6.5/10. Published 2026-03-11.
How severe is CVE-2026-3784?: Medium severity. CVSS v3 base score is 6.5 out of 10.