CVE-2026-70464 RsyncProject CVE debrief

Who should care

System administrators and security teams responsible for rsync daemon deployments should assess exposure and prioritize upgrading to version 3.5.0 or later. They must consider the potential impact on their deployments, verify exposure, and plan for upgrades or mitigations as necessary. This includes reviewing the current rsync daemon version, understanding the vulnerability's effects, and taking appropriate actions to prevent potential service disruption.

Why it matters

CVE-2026-70464 is a denial-of-service vulnerability in rsync daemon versions 2.0.0 before 3.5.0. Unaffected and affected users should assess exposure and prioritize upgrading to version 3.5.0 or later to prevent potential service disruption.

• Denial of service to legitimate clients
• Potential for service disruption
• Need for verification of exposure and remediation

Technical summary

The rsync daemon 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. This can be mitigated by upgrading to version 3.5.0 or later.

Defensive priority

Defenders should prioritize verifying exposure and upgrading to version 3.5.0 or later.

Recommended defensive actions

• Verify exposure by checking rsync daemon versions
• Upgrade to version 3.5.0 or later
• Monitor for potential denial-of-service attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its potential impact and affected versions. However, the exact scope of affected systems and potential impact require further verification by system administrators and security teams. They should check for rsync daemon versions 2.0.0 before 3.5.0, assess exposure, and prioritize upgrading to version 3.5.0 or later. Evidence of exposure includes unauthenticated remote attackers stalling the handshake process to exhaust daemon connection slots, denying service

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.