Description
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 that same host bypasses the TLS requirement and instead transmit data unencrypted.
Affected products
haxx: curl
References4
- curl.se/docs/CVE-2026-4873.html PatchVendor Advisory
- curl.se/docs/CVE-2026-4873.json Vendor Advisory
- www.openwall.com/lists/oss-security/2026/04/29/7 Mailing ListPatchThird Party Advisory
- hackerone.com/reports/3621851 ExploitIssue TrackingThird Party Advisory
Metrics
- CVSS 3.1
-
5.9
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - EPSS — exploit probability
- 0% percentile: 26 · as of 14 November 2026
- CWE
- CWE-319CWE-295
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.