What is CVE-2026-6253?

CVE-2026-6253 is a medium-severity vulnerability in Curl, classified under Insufficiently Protected Credentials. CVSS score: 5.9/10. Published 2026-05-13.

How severe is CVE-2026-6253?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Vulnerability in Curl

CVE-2026-6253

curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs…

EPSS: 0.000 (8.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Curl — versions 8.19.0, 8.18.0, 8.17.0
Haxx Curl

Weakness classification (CWE)

CWE-522 — Insufficiently Protected Credentials

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 (Patch, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2026-6253?: CVE-2026-6253 is a medium-severity vulnerability in Curl, classified under Insufficiently Protected Credentials. CVSS score: 5.9/10. Published 2026-05-13.
How severe is CVE-2026-6253?: Medium severity. CVSS v3 base score is 5.9 out of 10.