What’s Vulnerable › Vulnerabilities

CVE-2026-3784: wrong proxy connection reuse with credentials

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-11 · updated 2026-09-15
• Weakness: CWE-305

Description

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.

Affected products

• curl: from 7.7 before 8.18.0 — fixed in 8.18.0

How to fix

Upgrade to a fixed version: curl 8.18.0. Check the vendor advisory for mitigations.

References

• https://curl.se/docs/CVE-2026-3784.html
• https://curl.se/docs/CVE-2026-3784.json
• https://hackerone.com/reports/3584903
• http://www.openwall.com/lists/oss-security/2026/03/11/3
• https://cert-portal.siemens.com/productcert/html/ssa-253495.html

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