CVE intelligence

CVE-2026-9545

Vulnerability intelligence

Published Jul 3, 2026Sources checked Oct 28, 2026

7.5HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-9545 and is rated High severity with a CVSS score of 7.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Sep 28, 2026

USN-8487-1 fixed vulnerabilities in curl.

CISA KEVNot listedBased on the latest collected catalog

EPSS0.4%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is 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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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.

Source: NVD