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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
RsyncProject rsync unaffected
Version Status Constraints
3.4.2 affected ≤ 3.4.4
3.5.0 unaffected —

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Project Subscriptions

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/RsyncProject/rsync/releases/tag/v3.5.0 cve-icon cve-icon
https://github.com/RsyncProject/rsync/security/advisories/GHSA-rjvj-qgqg-cvx9 cve-icon cve-icon
https://www.vulncheck.com/advisories/rsync-dos-via-zt-zstandard-compression-thread-exhaustion cve-icon cve-icon
History

Thu, 13 Aug 2026 15:15:00 +0000

Type Values Removed Values Added
Description 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.
Title rsync 3.4.2 < 3.5.0 DoS via --zt Zstandard Compression Thread Exhaustion
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-08-13T14:45:11.164Z

Reserved: 2026-08-04T14:52:23.814Z

Link: CVE-2026-70455

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-13T15:19:59.197

Modified: 2026-08-13T15:19:59.197

Link: CVE-2026-70455

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-13T17:15:05Z

Weaknesses