CVE-2026-43617

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.

CVSS v3.1 Score

4.8

MEDIUM

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

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-289 CWE-289

Affected Products

Vendor	Product	Versions
samba	rsync	< 3.4.2

References

Advisories & Patches

https://github.com/RsyncProject/rsync/security/advisories/GHSA-rjfm-3w2m-jf4f

Other References

https://github.com/RsyncProject/rsync/releases/tag/v3.4.3 https://www.vulncheck.com/advisories/rsync-authorization-bypass-via-hostname-resolution

Frequently Asked Questions

What is CVE-2026-43617? +

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. It has a CVSS v3.1 base score of 4.8 (MEDIUM).

How severe is CVE-2026-43617? +

CVE-2026-43617 has a CVSS v3.1 score of 4.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-43617? +

CVE-2026-43617 affects products from samba, specifically: rsync. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-43617? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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