What is CVE-2026-4873?

CVE-2026-4873 is a medium-severity vulnerability in Curl, classified under Improper Certificate Validation. CVSS score: 5.9/10. Published 2026-05-13.

How severe is CVE-2026-4873?

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

Vulnerability in 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 th…

Vulnerability class: Improper Certificate Validation

EPSS: 0.000 (2.6th 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:H/I:N/A:N.

Affected products

Curl — versions 8.19.0, 8.18.0, 8.17.0
Haxx Curl

Weakness classification (CWE)

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-2026-4873?: CVE-2026-4873 is a medium-severity vulnerability in Curl, classified under Improper Certificate Validation. CVSS score: 5.9/10. Published 2026-05-13.
How severe is CVE-2026-4873?: Medium severity. CVSS v3 base score is 5.9 out of 10.