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

0.3

Exploit Probability

Published Date

2026-05-13

First Seen: 2026-05-17

📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 32.1% of all 365,987 vulnerabilities in our database.

#248,490

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 2026-09-15

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-319 CWE-295

📦 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-2026-13608	⚠️ high	7.4	0.6	A flaw in the libcurl SASL negotiation for LDAP authentication allows an incomplete handshake sequence to be misinterpre...	2026-09-06
CVE-2026-18924	⛔ critical	9.1	0.9	A flaw in libcurl's handling of HTTP/2 Server Push streams, when the parent handle is set to share connections with othe...	2026-09-06
CVE-2026-19931	⛔ critical	9.8	1.2	A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, w...	2026-09-06
CVE-2026-80229	⚠️ high	7.5	0.9	When performing transfers via libcurl’s multi interface, pooled TLS connections can outlive their originating easy han...	2026-09-06
CVE-2026-80230	⚠️ high	7.5	0.6	When `CURLOPT_PINNEDPUBLICKEY` is configured alongside options that disable standard peer verification (`CURLOPT_SSL_VER...	2026-09-06
CVE-2026-80231	⚠️ high	7.5	0.9	A flaw in libcurl makes it wrongly reuse an existing HTTPS connection setup for a given hostname even when using a diffe...	2026-09-06

These CVEs affect the same products