CVE-2026-53791: CWE-290 Authentication Bypass by Spoofing in RsyncProject rsync
rsync daemon before 3.5.0 contains an IP address spoofing vulnerability that allows unauthenticated remote attackers to bypass IP-based access controls by sending a crafted PROXY protocol header with a forged source address. Attackers who can connect directly to the rsync daemon can inject a spoofed source IP in the PROXY protocol header to circumvent hosts allow/deny rules, gaining unauthorized access that would otherwise be blocked based on their real source address.
AI Analysis
Technical Summary
The rsync daemon before version 3.5.0 contains an IP address spoofing vulnerability that permits unauthenticated remote attackers to bypass IP-based access controls. By sending a specially crafted PROXY protocol header with a forged source IP address, attackers can circumvent hosts allow/deny rules that rely on the real source address. This vulnerability is classified as CWE-290 (Authentication Bypass by Spoofing) and affects all versions up to and including 3.4.4.
Potential Impact
Attackers able to connect directly to the rsync daemon can inject a spoofed source IP address in the PROXY protocol header, bypassing IP-based access control rules. This leads to unauthorized access that would otherwise be blocked, potentially exposing sensitive data or allowing unauthorized operations via the rsync service.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or patch link is provided, users should monitor RsyncProject advisories for updates. Until a fix is available, consider restricting network access to the rsync daemon to trusted hosts only and disabling the PROXY protocol if it is not required.
CVE-2026-53791: CWE-290 Authentication Bypass by Spoofing in RsyncProject rsync
Description
rsync daemon before 3.5.0 contains an IP address spoofing vulnerability that allows unauthenticated remote attackers to bypass IP-based access controls by sending a crafted PROXY protocol header with a forged source address. Attackers who can connect directly to the rsync daemon can inject a spoofed source IP in the PROXY protocol header to circumvent hosts allow/deny rules, gaining unauthorized access that would otherwise be blocked based on their real source address.
CVSS v4.0
Score 9.1critical
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The rsync daemon before version 3.5.0 contains an IP address spoofing vulnerability that permits unauthenticated remote attackers to bypass IP-based access controls. By sending a specially crafted PROXY protocol header with a forged source IP address, attackers can circumvent hosts allow/deny rules that rely on the real source address. This vulnerability is classified as CWE-290 (Authentication Bypass by Spoofing) and affects all versions up to and including 3.4.4.
Potential Impact
Attackers able to connect directly to the rsync daemon can inject a spoofed source IP address in the PROXY protocol header, bypassing IP-based access control rules. This leads to unauthorized access that would otherwise be blocked, potentially exposing sensitive data or allowing unauthorized operations via the rsync service.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or patch link is provided, users should monitor RsyncProject advisories for updates. Until a fix is available, consider restricting network access to the rsync daemon to trusted hosts only and disabling the PROXY protocol if it is not required.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-06-10T20:14:32.827Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a7ddec4bf8831d5395cfc97
Added to database: 08/13/2026, 15:12:04 UTC
Last enriched: 08/13/2026, 15:45:17 UTC
Last updated: 08/13/2026, 19:21:07 UTC
Views: 4
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