What is CVE-2026-6276?

CVE-2026-6276 is a high-severity vulnerability in Curl, classified under Cleartext Transmission of Sensitive Information. CVSS score: 7.5/10. Published 2026-05-13.

How severe is CVE-2026-6276?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Curl

CVE-2026-6276

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information a…

EPSS: 0.000 (2.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/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-319 — Cleartext Transmission of Sensitive Information

References

2499f714-1537-4658-8207-48ae4bb9eae9 (Product)
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)

Frequently asked questions

What is CVE-2026-6276?: CVE-2026-6276 is a high-severity vulnerability in Curl, classified under Cleartext Transmission of Sensitive Information. CVSS score: 7.5/10. Published 2026-05-13.
How severe is CVE-2026-6276?: High severity. CVSS v3 base score is 7.5 out of 10.