CVE-2026-9545

In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate. When libcurl returns to the hostname the second time with a cached SSL session (`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the `CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might send off the second request's bytes on that new connection *before* enforcing the certificate verification failure. Potentially leaking sensitive information.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-9545.html	Patch Vendor Advisory
https://curl.se/docs/CVE-2026-9545.json	Vendor Advisory
https://hackerone.com/reports/3752888	Exploit Issue Tracking Third Party Advisory
https://hackerone.com/reports/3752888	Exploit Issue Tracking Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

History

07 Jul 2026, 15:03

Type	Values Removed	Values Added
CPE		cpe:2.3:a:haxx:curl::::::::
First Time		Haxx curl Haxx
CWE		NVD-CWE-noinfo
References	~~() https://curl.se/docs/CVE-2026-9545.html -~~	() https://curl.se/docs/CVE-2026-9545.html - Patch, Vendor Advisory
References	~~() https://curl.se/docs/CVE-2026-9545.json -~~	() https://curl.se/docs/CVE-2026-9545.json - Vendor Advisory
References	~~() https://hackerone.com/reports/3752888 -~~	() https://hackerone.com/reports/3752888 - Exploit, Issue Tracking, Third Party Advisory

06 Jul 2026, 18:16

Type	Values Removed	Values Added
References	~~() https://hackerone.com/reports/3752888 -~~	() https://hackerone.com/reports/3752888 -
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5

03 Jul 2026, 07:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-03 07:16

Updated : 2026-07-07 15:03

NVD link : CVE-2026-9545

Mitre link : CVE-2026-9545

CVE.ORG link : CVE-2026-9545

JSON object : View

Products Affected

haxx

curl

CWE

NVD-CWE-noinfo

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