Bug 2520159

Summary:	CVE-2026-70455 rsync: rsync: Denial of Service via Zstandard compression thread exhaustion [fedora-all]
Product:	[Fedora] Fedora	Reporter:	Srikanth Balasubramanian <sbalasub>
Component:	rsync	Assignee:	Michal Ruprich <mruprich>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	high
Version:	rawhide	CC:	luhliari, mruprich, ssorce
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["22a8aefa-b798-475c-9e59-cbc20c9b4918"]}
Fixed In Version:	rsync-3.5.0-1.fc44 rsync-3.5.0-1.fc43	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-08-22 01:24:45 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:	2515406

Description Srikanth Balasubramanian 2026-08-20 08:43:15 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.

rsync 3.4.2 before 3.5.0 contains a denial of service vulnerability that allows a remote sender to exhaust system resources by specifying the --zt short alias for --compress-threads, which bypasses the refuse options directive's string matching on long option names. Attackers can specify --zt=N with a large value to spawn an unbounded number of Zstandard worker threads on the receiver, exhausting available thread and memory resources.

Comment 1 Fedora Update System 2026-08-20 12:50:13 UTC

FEDORA-2026-bfae8723e2 (rsync-3.5.0-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-bfae8723e2

Comment 2 Fedora Update System 2026-08-20 12:50:42 UTC

FEDORA-2026-d6763b4c84 (rsync-3.5.0-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-d6763b4c84

Comment 3 Fedora Update System 2026-08-21 05:41:38 UTC

FEDORA-2026-bfae8723e2 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-bfae8723e2`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-bfae8723e2

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

Comment 4 Fedora Update System 2026-08-21 06:00:44 UTC

FEDORA-2026-d6763b4c84 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-d6763b4c84`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-d6763b4c84

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

Comment 5 Fedora Update System 2026-08-22 01:24:45 UTC

FEDORA-2026-bfae8723e2 (rsync-3.5.0-1.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 6 Fedora Update System 2026-08-27 01:11:32 UTC

FEDORA-2026-d6763b4c84 (rsync-3.5.0-1.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.