Bug 2496756 (CVE-2026-9545) - CVE-2026-9545 libcurl: libcurl: Information disclosure via cached SSL session and early data
Summary: CVE-2026-9545 libcurl: libcurl: Information disclosure via cached SSL session...
Keywords:
Status: NEW
Alias: CVE-2026-9545
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2509784 2497440
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-03 07:01 UTC by OSIDB Bzimport
Modified: 2026-08-19 13:28 UTC (History)
24 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

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Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:56869 0 None None None 2026-08-19 13:28:45 UTC

Description OSIDB Bzimport 2026-07-03 07:01:29 UTC 
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transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.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.
Comment 4 errata-xmlrpc 2026-08-19 13:28:43 UTC 
This issue has been addressed in the following products:

  Red Hat JBoss Core Services 2.4.62.SP5

Via RHSA-2026:56869 https://access.redhat.com/errata/RHSA-2026:56869
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