RsyncProject rsync up to 3.4.2 DNS lookup access control

Summaryinfo

A vulnerability labeled as critical has been found in RsyncProject rsync up to 3.4.2. This vulnerability affects unknown code of the component DNS lookup. Such manipulation leads to access control. This vulnerability is listed as CVE-2026-44507. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in RsyncProject rsync up to 3.4.2 and classified as critical. Affected by this issue is an unknown part of the component DNS lookup. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-44507 since 05/06/2026. The exploitation is known to be easy. The attack may be launched remotely. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1068.

Upgrading to version 3.4.3 eliminates this vulnerability.

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Productinfo

Type

• File Transfer Software

Vendor

• RsyncProject

Name

• rsync

Version

• 3.4.0
• 3.4.1
• 3.4.2

Website

• Product: https://github.com/RsyncProject/rsync/

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