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Fencer Vulns
medium 4.8

CVE-2026-43617 json

Rsync < 3.4.3 Authorization Bypass via Hostname Resolution

published 2026-05-20 5 mo ago modified 2026-11-08 25 h ago also EUVD-2026-31013 , GHSA-4j4q-473w-9q2r , JLSEC-2026-628

cvss
4.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia rsync_jll 3.4.4+0
  • RsyncProject rsync 3.4.3
  • rsync Debian 12 3.2.7-1+deb12u5
  • rsync Debian 13 3.4.1+ds1-5+deb13u3
  • rsync Debian 14 3.4.3+ds1-1

debian advisories DEBIAN-CVE-2026-43617

  • rsync Ubuntu 22.04 LTS 3.2.7-0ubuntu0.22.04.6
  • rsync Ubuntu 24.04 LTS 3.2.7-1ubuntu1.4
  • rsync Ubuntu 25.10 3.4.1+ds1-5ubuntu1.2
  • rsync Ubuntu 26.04 LTS 3.4.1+ds1-7ubuntu0.2
  • rsync Ubuntu Pro 14.04 LTS 3.1.0-2ubuntu0.4+esm3
  • rsync Ubuntu Pro 16.04 LTS 3.1.1-3ubuntu1.3+esm5
  • rsync Ubuntu Pro 18.04 LTS 3.1.2-2.1ubuntu1.6+esm3
  • rsync Ubuntu Pro 20.04 LTS 3.1.3-8ubuntu0.9+esm1

ubuntu advisories UBUNTU-CVE-2026-43617

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rsync SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.4.1-160000.6.1
  • rsync Linux Micro 6.0 3.2.7-8.1
  • rsync SLES for SAP applications 16.0, SLES 16.0 3.4.1-160000.4.1

suse advisories SUSE-SU-2026:23289-1SUSE-SU-2026:23323-1SUSE-SU-2026:23253-1SUSE-SU-2026:22015-1

  • rsync openSUSE Leap 16.0 3.4.1-160000.6.1
  • rsync openSUSE Tumbleweed 3.4.3-1.1

opensuse advisories openSUSE-SU-2026:21650-1openSUSE-SU-2026:10857-1

  • rsync Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 3.4.3-r0

alpine advisories ALPINE-CVE-2026-43617

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rsync Azure Linux 3.0 3.4.3-1

azure linux advisories AZL-86994

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-43617 updated cvss 4.2

rsync: rsync: Hostname-based ACL bypass in daemon chroot configuration

  • Red Hat Enterprise Linux 6 rsync Red Hat Enterprise Linux 7 rsync Red Hat Enterprise Linux 8 rsync, rsync-daemon Red Hat Enterprise Linux 9 rsync, rsync-daemon, rsync-rrsync
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 10 rsync
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-dashboard-rhel9
    under investigation

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
CNA 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
OSV 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
julia rsync_jll
<3.4.4+0
3.4.4+0

Affected products

  • RsyncProject rsync

Classification

Weakness
  • CWE-289 Authentication Bypass by Alternate Name

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.