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CVE-2026-70455— rsync 3.4.2 < 3.5.0 DoS via --zt Zstandard Compression Thread Exhaustion

Quick assessment

Affected
RsyncProject rsync
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

RsyncProject Rsync是RsyncProject组织开源的一款速度快、功能极其强大的文件复制工具，可用于复制远程文件和本地文件。 RsyncProject Rsync 3.4.2版本至3.5.0之前版本存在资源管理错误漏洞，该漏洞源于通过指定--zt短别名绕过refuse options指令对长选项名称的字符串匹配，可能导致远程攻击者指定大值生成无限制的Zstandard工作线程，耗尽系统线程和内存资源。

CVSS 7.5 · High EPSS 0.57% · P45

Affected Version Matrix 2

VendorProduct Version RangeStatus
RsyncProject rsync 3.4.2≤ 3.4.4 affected
3.5.0 unaffected
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I. Basic Information for CVE-2026-70455

Vulnerability Information
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Vulnerability Title
rsync 3.4.2 < 3.5.0 DoS via --zt Zstandard Compression Thread Exhaustion
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
RsyncProject Rsync 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
RsyncProject Rsync是RsyncProject组织开源的一款速度快、功能极其强大的文件复制工具，可用于复制远程文件和本地文件。 RsyncProject Rsync 3.4.2版本至3.5.0之前版本存在资源管理错误漏洞，该漏洞源于通过指定--zt短别名绕过refuse options指令对长选项名称的字符串匹配，可能导致远程攻击者指定大值生成无限制的Zstandard工作线程，耗尽系统线程和内存资源。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
RsyncProject rsync 3.4.2 ~ 3.4.4 -

II. Public POCs for CVE-2026-70455

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 8712 chars
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Trigger conditions & impact
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III. Intelligence Information for CVE-2026-70455

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Vendor Advisories for CVE-2026-70455 (2)

Vendor Pages for CVE-2026-70455 (1)

Same Patch Batch · RsyncProject · 2026-08-13 · 33 CVEs total

CVE-2026-53791 9.1 CRITICAL rsync < 3.5.0 Daemon IP Spoofing via PROXY Protocol Header
CVE-2026-70461 8.2 HIGH rsync 3.2.5 < 3.5.0 Heap Out-of-Bounds Write via files-from Entry
CVE-2026-70456 8.2 HIGH rsync 3.0.1 < 3.5.0 Heap Out-of-Bounds Write via read_args()
CVE-2026-70458 8.2 HIGH rsync 3.0.0 < 3.5.0 Out-of-Bounds Write via FLAG_HLINKED Handling
CVE-2026-70463 8.1 HIGH rsync 3.1.0 < 3.5.0 Authorization Bypass via auth users Directive Parsing
CVE-2026-53790 8.1 HIGH rsync < 3.5.0 Command Injection via Multiple Code Paths
CVE-2026-53795 8.1 HIGH rsync < 3.5.0 Arbitrary File Write via --temp-dir/--link-dest
CVE-2026-70460 8.1 HIGH rsync 2.3.3 < 3.5.0 Path Traversal via --partial-dir/--backup-dir Symlink
CVE-2026-53783 8.1 HIGH rsync < 3.5.0 TOCTOU Race Condition Directory Escape via rrsync
CVE-2026-70454 8.0 HIGH rsync < 3.5.0 TLS Certificate Validation Bypass via SSL/OpenSSL Mode
CVE-2026-53803 7.8 HIGH rsync < 3.5.0 Symlink Following Arbitrary File Overwrite
CVE-2026-70464 7.5 HIGH rsync 2.0.0 < 3.5.0 Connection Slot Exhaustion DoS via Handshake Stall
CVE-2026-70453 7.5 HIGH rsync < 3.5.0 Algorithmic Complexity DoS via hash_search()
CVE-2026-53793 7.4 HIGH rsync < 3.5.0 Path Confinement Bypass via /./ Boundary Marker in Chroot Mode
CVE-2026-70452 7.4 HIGH rsync 3.1.0 < 3.5.0 Access Control Bypass via DNS Resolution Failure
CVE-2026-53802 7.1 HIGH rsync < 3.5.0 Arbitrary File Read via Symlink Following
CVE-2026-53784 7.1 HIGH rsync < 3.5.0 Path Traversal via Symlink Module Root
CVE-2026-53785 7.1 HIGH rsync < 3.5.0 Path Traversal Write Escape via --relative Mode
CVE-2026-70457 6.5 MEDIUM rsync 3.2.3 < 3.5.0 Out-of-Bounds Write via parse_size_arg()
CVE-2026-53789 6.5 MEDIUM rsync < 3.5.0 Arbitrary File Deletion via Malicious File List

Showing top 20 of 33 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: rsync
Same vendor: RsyncProject
Same weakness: CWE-770

V. Comments for CVE-2026-70455

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