Bug 2509784 - CVE-2026-9545 curl: libcurl: Information disclosure via cached SSL session and early data [fedora-all]
Summary: CVE-2026-9545 curl: libcurl: Information disclosure via cached SSL session an...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Fedora
Classification: Fedora
Component: curl
Version: 45
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: ---
Assignee: Jan Macku
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard: {"flaws": ["9886f3a2-7f7e-40f5-b367-3...
Depends On:
Blocks: CVE-2026-9545
TreeView+ depends on / blocked
 
Reported: 2026-07-31 14:05 UTC by Tomas Hoger
Modified: 2026-08-31 17:03 UTC (History)
7 users (show)

Fixed In Version: curl-8.15.0-9.fc43
Clone Of:
Environment:
Last Closed: 2026-08-31 17:03:44 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)

Description Tomas Hoger 2026-07-31 14:05:47 UTC
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.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 1 Aoife Moloney 2026-08-17 15:44:21 UTC
This bug appears to have been reported against 'rawhide' during the Fedora Linux 45 development cycle.
Changing version to 45.

Comment 2 Fedora Update System 2026-08-25 08:52:51 UTC
FEDORA-2026-2f88b83676 (curl-8.18.0-9.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-2f88b83676

Comment 3 Fedora Update System 2026-08-26 02:01:58 UTC
FEDORA-2026-2f88b83676 has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-2f88b83676`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-2f88b83676

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 4 Fedora Update System 2026-08-27 00:55:34 UTC
FEDORA-2026-2f88b83676 (curl-8.18.0-9.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 5 Fedora Update System 2026-08-27 16:18:51 UTC
FEDORA-2026-f903f9ff11 (curl-8.15.0-9.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-f903f9ff11

Comment 6 Fedora Update System 2026-08-28 01:37:17 UTC
FEDORA-2026-f903f9ff11 has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-f903f9ff11`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-f903f9ff11

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 7 Fedora Update System 2026-08-31 17:03:44 UTC
FEDORA-2026-f903f9ff11 (curl-8.15.0-9.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.


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