Improper access control in Rsync - CVE-2026-43617

Vulnerability identifier: #VU133145

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-43617

CWE-ID: CWE-284

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to bypass hostname-based access controls.

The vulnerability exists due to improper access control in reverse-DNS lookup handling in rsync daemon mode when processing connections after entering the daemon chroot. A remote attacker can connect from a denied hostname and cause hostname-based deny rules to fail open to bypass hostname-based access controls.

Only daemon configurations with daemon chroot = /X are affected when the chroot tree lacks DNS resolution support. IP-based ACLs are unaffected.

Rsync
Gentoo Linux
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
Debian Linux
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Micro
Ubuntu
Basesystem Module
openSUSE Leap
Fedora
LANTIME Operating System Firmware (LTOS)
rsync (Ubuntu package)
rsync
rsync-debuginfo
rsync-debugsource
rsync (Debian package)
net-misc/rsync

Install security update from vendor's website.

Rsync - update to 3.4.3
LANTIME Operating System Firmware (LTOS) - update to 7.10.012
rsync (Ubuntu package) - addressed in versions 3.1.0-2ubuntu0.4+esm3, 3.1.0-2ubuntu0.4+esm4, 3.1.1-3ubuntu1.3+esm5, 3.1.1-3ubuntu1.3+esm6, 3.1.2-2.1ubuntu1.6+esm3, 3.1.2-2.1ubuntu1.6+esm4, 3.1.3-8ubuntu0.9+esm1, 3.1.3-8ubuntu0.9+esm2, 3.2.7-0ubuntu0.22.04.6, 3.2.7-0ubuntu0.22.04.7, 3.2.7-1ubuntu1.4, 3.2.7-1ubuntu1.5, 3.4.1+ds1-7ubuntu0.2, 3.4.1+ds1-7ubuntu0.3, 3.4.1+ds1-5ubuntu1.2, 3.4.1+ds1-5ubuntu1.3
rsync - addressed in versions 3.1.3-3.43.1, 3.2.3-150400.3.31.1, 3.2.7-7.1, 3.2.7-150600.3.21.1, 3.3.0-slfo.1.1_6.1
rsync-debuginfo - addressed in versions 3.1.3-3.43.1, 3.2.3-150400.3.31.1, 3.2.7-7.1, 3.2.7-150600.3.21.1, 3.3.0-slfo.1.1_6.1
rsync-debugsource - addressed in versions 3.1.3-3.43.1, 3.2.3-150400.3.31.1, 3.2.7-7.1, 3.2.7-150600.3.21.1, 3.3.0-slfo.1.1_6.1
rsync (Debian package) - addressed in versions 3.2.7-1+deb12u5, 3.4.1+ds1-5+deb13u3
net-misc/rsync - update to 3.4.3
rsync - addressed in versions 3.4.3-1.fc43, 3.4.3-1.fc44, 3.4.4-1.fc43

• https://github.com/RsyncProject/rsync/pull/895/changes/8471fdd1561049ef5f58df44a1811a50bd9a531d#diff-51920e95310ebfbc1ae31709f3b95f89afffbf4f1a6e38e8b2b406e2fb6197ea

• Multiple vulnerabilities in Rsync
• Debian update for rsync
• Fedora 44 update for rsync
• Fedora 43 update for rsync
• SUSE update for rsync
• SUSE update for rsync
• SUSE update for rsync
• SUSE update for rsync
• SUSE update for rsync
• Ubuntu update for rsync
• Ubuntu update for rsync
• Ubuntu update for rsync
• Fedora 44 update for rsync
• Fedora 43 update for rsync
• Ubuntu update for rsync
• Gentoo update for rsync
• Multiple vulnerabilities in Meinberg LANTIME Operating System Firmware