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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.

PUBLISHED Reserved 2026-05-01 | Published 2026-05-20 | Updated 2026-05-20 | Assigner VulnCheck




MEDIUM: 6.3CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

MEDIUM: 4.8CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem types

Authentication Bypass by Alternate Name

Product status

Default status
unaffected

Any version before 3.4.3
affected

Credits

Joshua Rogers (@MegaManSec) finder

References

github.com/.../rsync/security/advisories/GHSA-rjfm-3w2m-jf4f vendor-advisory

github.com/RsyncProject/rsync/releases/tag/v3.4.3 release-notes

www.vulncheck.com/...rization-bypass-via-hostname-resolution third-party-advisory

cve.org (CVE-2026-43617)

nvd.nist.gov (CVE-2026-43617)

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