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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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade curl | Jul 6, 2026 | Jul 3, 2026 |
| Amazon_linux_2023 | — | Upgrade libcurl-debuginfoUpgrade curl-minimal-debuginfoUpgrade curl-debuginfoUpgrade libcurl-minimalUpgrade curl-debugsourceUpgrade libcurl-develUpgrade curlUpgrade curl-minimalUpgrade libcurlUpgrade libcurl-minimal-debuginfo | Sep 30, 2026 | Jul 3, 2026 |
| Redhat_linux | — | No solution exists | Oct 19, 2026 | Jul 3, 2026 |
| Splunk | — | Upgrade Splunk Enterprise to version 10.4.3Upgrade Splunk Enterprise to version 10.0.10Upgrade Splunk Enterprise to version 10.2.7Upgrade Splunk Enterprise to version 9.4.15 | Oct 20, 2026 | Jul 3, 2026 |
| Ubuntu | — | Upgrade libcurl4-gnutls-devUpgrade libcurl4-openssl-devUpgrade libcurl4-gnutls-dev (Ubuntu Pro)Upgrade libcurl4t64Upgrade libcurl4Upgrade libcurl4 (Ubuntu Pro)Upgrade libcurl3-gnutls (Ubuntu Pro)Upgrade libcurl3 (Ubuntu Pro)Upgrade libcurl3-gnutlsUpgrade libcurl4-nss-dev (Ubuntu Pro)Upgrade libcurl4-nss-devUpgrade libcurl3t64-gnutlsUpgrade libcurl3-nss (Ubuntu Pro)Upgrade curlUpgrade curl (Ubuntu Pro)Upgrade libcurl4-openssl-dev (Ubuntu Pro)Upgrade libcurl3-nss | Jul 1, 2026 | Jun 30, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Aug 10, 2026 | Jul 3, 2026 |
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