Skip to main content

rsync EUVDEUVD-2026-58099

| CVE-2026-53791 CRITICAL
Authentication Bypass by Spoofing (CWE-290)
2026-08-13 VulnCheck
Critical
Disputed · 9.1 Vendor: VulnCheck
Share

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
Red Hat
7.4 HIGH
qualitative

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

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. There is no public exploit identified at time of analysis and it is not listed in CISA KEV, but the CVSS 4.0 base score of 9.1 reflects high confidentiality and integrity impact once the IP allowlist is circumvented.

Technical ContextAI

The rsync daemon (rsyncd) enforces network access with 'hosts allow' / 'hosts deny' rules evaluated against the client's source IP. When configured to speak the HAProxy PROXY protocol - used so rsyncd can recover the real client IP when it sits behind a load balancer or reverse proxy - the daemon reads the source address from the PROXY header line prepended to the TCP stream rather than from the kernel socket. This is a textbook CWE-290 (Authentication Bypass by Spoofing) issue: the daemon trusts an attacker-supplied assertion of identity (the header) instead of a cryptographically or network-verified source. Any client able to reach the listening port directly can therefore assert an arbitrary 'trusted' IP. Affected code is the rsync package identified by cpe:2.3:a:rsyncproject:rsync:*, with the corrective logic shipped in v3.5.0.

RemediationAI

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. If you cannot patch immediately, the most effective compensating control is to disable PROXY protocol trust in rsyncd.conf so the daemon uses the real socket source IP again - the trade-off is that a fronting proxy will then present its own IP, breaking any allow/deny rules that depend on the true client address. Alternatively, ensure rsyncd is not directly reachable by untrusted clients: place it strictly behind the trusted proxy/load balancer using firewall rules that permit inbound connections to the rsync port (typically 873) only from the proxy's address, so no attacker can inject a forged PROXY header directly. As defense in depth, avoid relying on IP-based hosts allow/deny as the sole access control and add authenticated modules (secrets file) where feasible. Consult GHSA-h2q9-5fr8-w635 and the VulnCheck advisory for configuration specifics.

More in Rsync

View all
CVE-2024-12085 HIGH POC
7.5 Jan 14

A flaw was found in rsync which could be triggered when rsync compares file checksums. Rated high severity (CVSS 7.5), t

CVE-2024-12084 CRITICAL POC
9.8 Jan 15

A heap-based buffer overflow flaw was found in the rsync daemon. Rated critical severity (CVSS 9.8), this vulnerability

CVE-2014-9512 MEDIUM POC
6.4 Feb 12

rsync 3.1.1 allows remote attackers to write to arbitrary files via a symlink attack on a file in the synchronization pa

CVE-2024-12087 HIGH POC
7.5 Jan 14

Server-to-client path traversal in rsync lets a malicious or compromised rsync server write files outside the client's i

CVE-2022-29154 HIGH POC
7.4 Aug 02

An issue was discovered in rsync before 3.2.5 that allows malicious remote servers to write arbitrary files inside the d

CVE-2014-2855 HIGH
7.8 Apr 23

The check_secret function in authenticate.c in rsync 3.1.0 and earlier allows remote attackers to cause a denial of serv

CVE-2024-12086 MEDIUM POC
6.8 Jan 14

A flaw was found in rsync. Rated medium severity (CVSS 6.1), this vulnerability is remotely exploitable, no authenticati

CVE-2017-16548 CRITICAL
9.8 Nov 06

The receive_xattr function in xattrs.c in rsync 3.1.2 and 3.1.3-development does not check for a trailing '\0' character

CVE-2017-17434 CRITICAL
9.8 Dec 06

The daemon in rsync 3.1.2, and 3.1.3-development before 2017-12-03, does not check for fnamecmp filenames in the daemon_

CVE-2017-15994 CRITICAL
9.8 Oct 29

rsync 3.1.3-development before 2017-10-24 mishandles archaic checksums, which makes it easier for remote attackers to by

CVE-2026-53790 CRITICAL
9.2 Aug 13

Arbitrary command execution in rsync before 3.5.0 arises from multiple unsanitized code paths - the RSYNC_CONNECT_PROG e

CVE-2026-70460 CRITICAL
9.2 Aug 13

Arbitrary file write in rsync 2.3.3 through 3.4.4 lets a malicious sender escape a daemon module's root by abusing symli

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

Share

EUVD-2026-58099 vulnerability details – vuln.today

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy