CVE-2026-9545 | exposing HTTP/3 early data

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

Published: 2026-07-03 Last update: 2026-07-03 Assigner: 2499f714-1537-4658-8207-48ae4bb9eae9 Source: 2499f714-1537-4658-8207-48ae4bb9eae9
NVD Status：Received，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-9545 is rated Low Risk (3.2/100): low exploitation likelihood (EPSS 0.13%). Low composite risk—no urgent action required; patch on your normal maintenance cycle and revisit priority if CVSS or EPSS increases.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-9545

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-04 — 0.13% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-9545

CVSS metrics for this CVE.

No CVSS data in dataset for this CVE.

Weakness enumeration for CVE-2026-9545

GitHub Security Advisory for CVE-2026-9545

GHSA-6v72-wfcj-jv53 · Severity: unknown — In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when...

OS Trackers for CVE-2026-9545

vendor priority summary link
debian unimportant CVE-2026-9545 unimportant priority: Debian including 1 source packages (curl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2. https://security-tracker.debian.org/tracker/CVE-2026-9545
ubuntu low CVE-2026-9545 low priority: Ubuntu including 1 source packages (curl), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): not-affected 6, released 2, pending 1. https://ubuntu.com/security/CVE-2026-9545

Affected software / configurations for CVE-2026-9545

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-9545

cvelogic Threat Intelligence