Bug 2509784

Summary:	CVE-2026-9545 curl: libcurl: Information disclosure via cached SSL session and early data [fedora-all]
Product:	[Fedora] Fedora	Reporter:	Tomas Hoger <thoger>
Component:	curl	Assignee:	Jan Macku <jamacku>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	45	CC:	jamacku, jmigacz, kdudka, lzaoral, msekleta, paul, vmihalko
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["9886f3a2-7f7e-40f5-b367-3b9043f51dc2"]}
Fixed In Version:	curl-8.15.0-9.fc43	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-08-31 17:03:44 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2496756

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transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.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.