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CVE-2026-43617

Rsync < 3.4.3 Authorization Bypass via Hostname Resolution

Published: May 20, 2026Updated: May 21, 2026 Sources: CVE List NVDCWE-289
NVD MITRE
4.8CVSSMEDIUM
EPSS Score
0.3%
Top 79.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

Rsync version 3.4.2 and prior contain an authorization bypass vulnerability in the rsync daemon's hostname-based access control list enforcement when configured with chroot. Attackers can bypass hostname-based deny rules by controlling the PTR record for their source IP address, allowing connections from hostnames that administrators intended to deny when reverse DNS resolution fails and defaults to UNKNOWN.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:LI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-289

Affected Products

rsyncRsyncProject
Library
OSS Libraries / generic-library
rsyncsamba
On-prem
OSS Libraries / generic-library
rsyncprojectoss-projectOSS Librariesaka rsync, rsync project
sambaoss-projectDEOperating Systems

Exploitability

Official Patch Available

References

https://github.com/RsyncProject/rsync/security/advisories/GHSA-rjfm-3w2m-jf4f
github.com
https://github.com/RsyncProject/rsync/releases/tag/v3.4.3
github.com
https://www.vulncheck.com/advisories/rsync-authorization-bypass-via-hostname-resolution
vulncheck.com

Timeline

Published
May 20, 2026
Last Updated
May 21, 2026

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