CVE-2026-9545

HIGH

curl - Exposing HTTP/3 Early Data

Title source: rule
STIX 2.1

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

Scores

CVSS v3 7.5
EPSS 0.0041
EPSS Percentile 32.9%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable yes
Technical Impact partial

Details

Status published
Products (14)
curl/curl 8.11.0
curl/curl 8.11.1
curl/curl 8.12.0
curl/curl 8.12.1
curl/curl 8.13.0
curl/curl 8.14.0
curl/curl 8.14.1
curl/curl 8.15.0
curl/curl 8.16.0
curl/curl 8.17.0
... and 4 more
Published Jul 03, 2026
Tracked Since Jul 03, 2026