CVE-2026-4873

🔶 medium

Summary

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.

CVSS Score

5.9

Medium

EPSS Score

0.0

Exploit Probability

Published Date

2026-05-13

First Seen: 2026-05-17

📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 33.3% of all 329,456 vulnerabilities in our database.

#219,613

Below average severity

Severity Percentile

🎯 CISA SSVC Assessment Updated: May 13, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

Requires human interaction

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

Arkadi Vainbrand Daniel Stenberg (remediation developer)

SSVC data provided by CISA

Last Modified 2026-05-14

Source NVD 🔗

CVSS Vector 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CWE IDs (Weakness Types)

CWE-295 CWE-319

📦 Affected Products 1

Vendor	Product	Status	Affected Versions
haxx	curl	Affected	> 7.20.0 < 8.20.0

🔗 References 4

https://curl.se/docs/CVE-2026-4873.html

Patch Vendor Advisory

https://curl.se/docs/CVE-2026-4873.json

Vendor Advisory

https://hackerone.com/reports/3621851

Exploit Issue Tracking Third Party Advisory

http://www.openwall.com/lists/oss-security/2026/04/29/7

Mailing List Patch Third Party Advisory

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-6253	🔶 medium	5.9	0.0	curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following cond...	2026-05-13
CVE-2026-6276	⚠️ high	7.5	0.0	Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done u...	2026-05-13
CVE-2026-6429	🔶 medium	5.3	0.0	When asked to both use a `.netrc` file for credentials and to follow HTTP redirects, libcurl could leak the password use...	2026-05-13
CVE-2026-7009	🔶 medium	5.3	0.0	When curl is told to use the Certificate Status Request TLS extension, often referred to as OCSP stapling, to verify t...	2026-05-13
CVE-2026-7168	🔶 medium	5.3	0.1	Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with Digest authentication and the...	2026-05-13
CVE-2026-1965	🔶 medium	6.5	0.1	libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS r...	2026-03-11

These CVEs affect the same products