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rsync CVE-2026-53791

| EUVDEUVD-2026-58099 CRITICAL
Authentication Bypass by Spoofing (CWE-290)
2026-08-13 VulnCheck
Critical
Disputed · 9.1 Vendor: VulnCheck
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Severity by source

Sources disagree (Medium–Critical)
Vendor (VulnCheck) PRIMARY
9.1 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/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
vuln.today AI
7.4 HIGH

Network vector, no auth or interaction, but AC:H because the daemon must be configured to trust PROXY protocol; high confidentiality/integrity from bypassed access controls, no availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
6.5 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Source Code Evidence Fetched
Aug 13, 2026 - 15:54 vuln.today
Analysis Generated
Aug 13, 2026 - 15:54 vuln.today
CVE Published
Aug 13, 2026 - 14:38 cve.org
CRITICAL 9.1

DescriptionCVE.org

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.

AnalysisAI

IP-based access control bypass in the rsync daemon (rsyncproject/rsync) before version 3.5.0 lets unauthenticated remote attackers forge their source address by injecting a crafted PROXY protocol header, defeating hosts allow/deny restrictions. Reported by VulnCheck and fixed in the v3.5.0 major security release, the flaw applies to daemons that trust PROXY protocol headers yet accept direct client connections. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Connect directly to rsync daemon port
Delivery
Prepend forged PROXY protocol header
Exploit
Assert allowlisted source IP
Execution
Bypass hosts allow/deny checks
Impact
Access restricted rsync modules and data

Vulnerability AssessmentAI

Exploitation Exploitation requires that the rsync daemon (before 3.5.0) be configured to trust the HAProxy PROXY protocol (i.e., it parses a client-supplied PROXY header to determine the source IP) AND that the attacker can open a direct TCP connection to that daemon rather than being forced through the legitimate fronting proxy. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor CVSS 4.0 vector (AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N) rates this 9.1 (Critical): network reachable, low complexity, no privileges or user interaction, with high confidentiality and integrity impact but no availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker who can reach a PROXY-protocol-enabled rsync daemon directly opens a TCP connection and prepends a forged PROXY header claiming a source IP that appears in the daemon's 'hosts allow' list. The daemon honors the spoofed address, grants access that the attacker's real IP would have been denied, and permits reading or writing of exposed rsync modules. …
Remediation Upgrade to the Vendor-released patch: rsync 3.5.0, a designated major security release (https://github.com/RsyncProject/rsync/releases/tag/v3.5.0), which is the primary and recommended fix. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, identify all systems running rsync daemon versions prior to 3.5.0, especially production systems handling sensitive data. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected
SUSE Linux Enterprise Micro 5.3 Affected

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CVE-2026-53791 vulnerability details – vuln.today

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