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rsync CVE-2026-53794

| EUVDEUVD-2026-58033 MEDIUM
Improper Validation of Specified Quantity in Input (CWE-1284)
2026-08-13 VulnCheck
6.9
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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
7.5 HIGH

Network-accessible with no authentication required and no user interaction; unbounded memory allocation can exhaust host memory, warranting A:H despite the CVSS 4.0 input rating VA:L.

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

Primary rating from Vendor (VulnCheck).

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 - 16:07 vuln.today
Analysis Generated
Aug 13, 2026 - 16:07 vuln.today
CVE Published
Aug 13, 2026 - 14:39 cve.org
MEDIUM 6.9

DescriptionCVE.org

rsync before 3.5.0 contains a logic error in --max-alloc handling that allows a sender or configuration setting --max-alloc=0 to disable allocation sanity checks entirely rather than enforcing a zero-byte cap. Attackers can exploit this flaw to cause the receiver to attempt unbounded memory allocations for file list and data structures, potentially exhausting available memory and causing a denial of service.

AnalysisAI

Memory exhaustion in rsync before 3.5.0 exposes receivers to remote denial of service through a logic error in --max-alloc handling, where passing --max-alloc=0 silently disables all allocation sanity checks instead of enforcing a zero-byte cap. Any rsync receiver reachable from an untrusted sender - including public mirrors and unauthenticated daemons - is at risk, as the CVSS 4.0 vector (AV:N/AC:L/PR:N/UI:N) confirms no authentication or special conditions are required to trigger the flaw. No active exploitation has been confirmed in CISA KEV and no public exploit code has been identified at time of analysis, though the trivial trigger condition makes this a credible remote DoS threat against exposed rsync endpoints.

Technical ContextAI

rsync is a delta-compression file synchronization utility, identified via CPE cpe:2.3:a:rsyncproject:rsyncproject:rsync. The --max-alloc option is designed to impose an upper bound on individual memory allocations within the rsync data pipeline, protecting the receiver from processing maliciously oversized file lists or data structures sent by a sender. The logic error, classified under CWE-1284 (Improper Validation of Specified Quantity in Input), arises because the code interprets --max-alloc=0 as 'uncapped' (no limit) rather than 'zero bytes allowed,' inverting the intended semantics. Once the cap is disabled, the receiver allocates memory directly proportional to attacker-supplied values in the file list and transfer data structures, with no upper bound enforced. This is a pure logic flaw - not a memory corruption issue - meaning exploitation is stable and reliable without triggering crashes from invalid memory writes.

RemediationAI

Vendor-released patch: v3.5.0. Upgrade rsync to version 3.5.0 or later, available at https://github.com/RsyncProject/rsync/releases/tag/v3.5.0, with full details in the security advisory at https://github.com/RsyncProject/rsync/security/advisories/GHSA-p827-vwcp-m964. Where immediate upgrading is not feasible, restrict network access to rsync daemons (default TCP port 873) using firewall rules or host-based ACLs to limit connections to trusted sender IP ranges, which eliminates the remote exploitation path at the cost of reducing accessibility for legitimate clients. Auditing all rsync configuration files and wrapper scripts to remove any explicit --max-alloc=0 arguments closes the configuration-based trigger, though a malicious remote sender can still supply this flag during an active session. Enabling memory usage monitoring and alerting on rsync receiver processes can provide early warning of exploitation attempts.

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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-2026-53794 vulnerability details – vuln.today

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