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rsync EUVDEUVD-2026-58051

| CVE-2026-70453 HIGH
Inefficient Algorithmic Complexity (CWE-407)
2026-08-13 VulnCheck
8.7
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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-reachable with no auth or complexity prerequisites; impact is CPU exhaustion on the receiver (availability only); no confidentiality or integrity impact; scope unchanged as only the receiver process is affected.

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
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat
6.5 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 - 15:45 vuln.today
Analysis Generated
Aug 13, 2026 - 15:45 vuln.today
CVE Published
Aug 13, 2026 - 14:46 cve.org
HIGH 8.7

DescriptionCVE.org

rsync before 3.5.0 contains an algorithmic complexity vulnerability in the hash_search() function that allows a remote attacker to cause a denial of service by delivering a carefully constructed file list. A sender can exploit the quadratic-time worst-case behavior in hash lookups to exhaust receiver CPU resources with a modest number of crafted entries, causing a sustained denial of service.

AnalysisAI

CPU exhaustion in rsync receivers before 3.5.0 allows a remote sender to cause denial of service by exploiting quadratic-time worst-case behavior in the hash_search() function (CWE-407). A malicious or compromised sender delivers a carefully crafted file list - requiring only a modest number of entries - to collapse hash lookup performance and sustain receiver CPU exhaustion for the duration of the sync session. No public exploit has been identified at time of analysis, but the unauthenticated network attack vector and rsync's ubiquitous deployment in backup and file-synchronization infrastructure make patch urgency high.

Technical ContextAI

rsync implements a delta-transfer algorithm that relies on rolling checksums and hash tables to match file blocks between sender and receiver. The affected component, hash_search(), performs hash-based lookups over file list entries during the matching phase. CWE-407 (Insufficient Algorithmic Complexity) describes flaws where an algorithm degrades from expected O(n) to O(n²) or worse under adversarially chosen input - typically via hash collision chains that force linear probing through the entire table for every lookup. A sender controlling the file list content can select entry names or metadata that produce worst-case hash collisions in the receiver's table, turning a normally fast operation into a CPU-intensive traversal. The CPE cpe:2.3:a:rsyncproject:rsync:*:*:*:*:*:*:*:* covers all versions prior to 3.5.0 across all platforms. The attack is protocol-native: no out-of-band channel or memory corruption is required - only valid rsync protocol messages with crafted content.

RemediationAI

Upgrade rsync to version 3.5.0 or later; this is the vendor-released patch confirmed by the RsyncProject GitHub release tag and security advisory GHSA-8x5r-mjx8-83hv (https://github.com/RsyncProject/rsync/releases/tag/v3.5.0). If immediate upgrade is not feasible, restrict rsync receiver access to known, trusted sender IP addresses using firewall ACLs or the hosts allow directive in rsyncd.conf - this reduces the attacker pool but does not eliminate risk from compromised trusted hosts and requires accurate IP allowlisting. Rate-limiting incoming rsync connections at the network perimeter (e.g., iptables connlimit or fail2ban) raises the cost of sustaining the DoS but does not prevent a single malicious session from exhausting CPU during its lifetime. Running the rsync receiver process with reduced scheduling priority (nice +10 or systemd CPUWeight) limits collateral damage to co-located services but does not prevent the DoS itself. None of these workarounds address the root cause - patching to 3.5.0 is the only definitive fix.

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Vendor StatusVendor

SUSE

Severity: Important
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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EUVD-2026-58051 vulnerability details – vuln.today

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