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rsync daemon CVE-2026-70464

| EUVDEUVD-2026-58040 HIGH
Allocation of Resources Without Limits or Throttling (CWE-770)
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 authentication or user interaction required; impact is availability-only with no scope change beyond the daemon process.

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
7.5 HIGH
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 - 15:39 vuln.today
Analysis Generated
Aug 13, 2026 - 15:39 vuln.today
CVE Published
Aug 13, 2026 - 14:41 cve.org
HIGH 8.7

DescriptionCVE.org

rsync daemon 2.0.0 before 3.5.0 contains a denial of service vulnerability that allows unauthenticated remote attackers to exhaust daemon connection slots by stalling the handshake process before or after module selection without triggering the I/O timeout. Attackers can open many simultaneous connections and trickle data at the minimum rate to avoid timeout, or stall entirely before module selection where no timeout applies, consuming all available connection slots and denying service to legitimate clients.

AnalysisAI

Connection slot exhaustion in rsync daemon versions 2.0.0 through 3.4.x allows unauthenticated remote attackers to deny service to legitimate clients by stalling the protocol handshake across two distinct vectors. Pre-module-selection stalls are unconditionally effective because the daemon applies no timeout in that phase; post-module-selection, attackers can trickle data just above the I/O timeout floor to hold slots indefinitely while never completing the handshake. No public exploit identified at time of analysis, though the attack is trivially scriptable and requires no authentication or prior access.

Technical ContextAI

rsync is a widely deployed file synchronization utility that, in daemon mode (rsyncd), accepts TCP connections and processes a two-phase handshake: a pre-module-selection phase where the client identifies which module (share) to access, and a post-module-selection phase where data transfer negotiation occurs. CWE-770 (Allocation of Resources Without Limits or Throttling) is the root cause: the daemon allocates a connection slot on TCP accept but enforces no timeout during the pre-module-selection phase, and the existing I/O timeout in the post-module-selection phase can be evaded by sending data at just above the minimum threshold. The affected CPE is cpe:2.3:a:rsyncproject:rsync:*:*:*:*:*:*:*:*, covering all rsync versions from 2.0.0 up to but not including 3.5.0, confirmed by the GitHub release comparing v3.4.4 to v3.5.0.

RemediationAI

Upgrade rsync to version 3.5.0 or later, confirmed as a major security release addressing this vulnerability; the release is available at https://github.com/RsyncProject/rsync/releases/tag/v3.5.0 with full changelog at https://download.samba.org/pub/rsync/NEWS#3.5.0. If immediate patching is not feasible, the most effective compensating control is restricting rsyncd exposure to trusted source IP ranges via firewall rules or the hosts allow directive in rsyncd.conf - this eliminates the attack surface entirely for untrusted networks, though it will break legitimate access from outside those ranges. Additionally, lowering the max connections value in rsyncd.conf reduces the pool size available to exhaust, but does not prevent exhaustion - it only slows the attack and simultaneously degrades legitimate capacity. Neither workaround addresses the pre-module-selection stall vector at the protocol level; only the v3.5.0 patch resolves that root cause.

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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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CVE-2026-70464 vulnerability details – vuln.today

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