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7.5High

CVE-2026-9545exposing HTTP/3 early data

curl curl Published: (4 months ago)

Description

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

Weakness (CWE): CWE-200

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

VendorProductVersions
curl curl 8.11.0 – < 8.14.2, 8.15.0 – < 8.16.1, 8.17.0 – < 8.20.1
haxx curl 8.11.0 – < 8.21.0

References and patches

CPE matches (NVD) (1)
  • cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:* ≥ 8.11.0 < 8.21.0

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