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CVE-2026-9545

exposing HTTP/3 early data

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 8.14.2, 8.16.1, 8.20.1
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: poc
  • Automatable: yes
  • Technical impact: partial

Summary

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: poc · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • curl curl

    From 8.11.0 · fixed in 8.14.2; From 8.15.0 · fixed in 8.16.1; From 8.17.0 · fixed in 8.20.1

  • curl curl

    Version range not reported

  • curl curl

    8.20.0, 8.19.0, 8.18.0, 8.17.0, 8.16.0, 8.15.0, 8.14.1, 8.14.0, 8.13.0, 8.12.1, 8.12.0, 8.11.1, 8.11.0

References 3

curl.se

hackerone.com