Description
Rsync is a file-copying tool that uses a delta-transfer algorithm to synchronize remote and local files. In versions prior to 3.4.3, when using a daemon configured with a chroot, the reverse DNS lookup of the connecting client was performed after the chroot had been entered. If the chroot did not contain the files glibc needs for resolution (/etc/resolv.conf, /etc/nsswitch.conf,
/etc/hosts, NSS service modules), the lookup failed and the connecting hostname was set to "UNKNOWN". Hostname-based deny rules ("hosts deny = *.evil.example") therefore could not match, and an attacker who controlled the PTR record for their source IP could connect from a hostname that the administrator had intended to deny. IP-based ACLs ("hosts allow = 10.0.0.0/8") are unaffected. This issue is fixed in version 3.4.3.
Published: 2026-07-20
Score: 4.8 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Mon, 20 Jul 2026 21:00:00 +0000

Type Values Removed Values Added
Description Rsync is a file-copying tool that uses a delta-transfer algorithm to synchronize remote and local files. In versions prior to 3.4.3, when using a daemon configured with a chroot, the reverse DNS lookup of the connecting client was performed after the chroot had been entered. If the chroot did not contain the files glibc needs for resolution (/etc/resolv.conf, /etc/nsswitch.conf, /etc/hosts, NSS service modules), the lookup failed and the connecting hostname was set to "UNKNOWN". Hostname-based deny rules ("hosts deny = *.evil.example") therefore could not match, and an attacker who controlled the PTR record for their source IP could connect from a hostname that the administrator had intended to deny. IP-based ACLs ("hosts allow = 10.0.0.0/8") are unaffected. This issue is fixed in version 3.4.3.
Title Rsync: hostname/ACL bypass on DNS-lookup failure
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-20T20:29:26.577Z

Reserved: 2026-05-06T18:28:20.886Z

Link: CVE-2026-44507

cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses