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CWE-290Weakness · CWE-290

CVE-2026-53791

CRITICAL · 9.1 CVSS v3.1 Developing Published 2026-08-13
No fix yet
No fix has been published. The vendor has not shipped a fixed release or patch. You remain exposed.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 8 days old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-27.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Recommended fix Moderate confidence

rsync 3.5.0 or later

  1. 1. Identify the currently installed rsync version by running 'rsync --version'
  2. 2. If running a version before 3.5.0, obtain the latest stable rsync release (3.5.0 or later) from your operating system's package manager or from rsync.samba.org
  3. 3. Upgrade rsync to version 3.5.0 or later using your system's package manager (e.g., 'apt-get update && apt-get install rsync' for Debian/Ubuntu, or 'yum update rsync' for RHEL/CentOS)
  4. 4. After upgrading, verify the new version with 'rsync --version' to confirm the installation was successful
  5. 5. If using rsync in daemon mode with PROXY protocol support, ensure that your hosts allow/deny rules are still properly configured as a defense-in-depth measure
  6. 6. Test that the rsync daemon starts correctly and accepts connections from expected clients

Generated from the published advisory — verify against the referenced sources before acting.

No vendor fix exists The vendor has not published a patch for this.

There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53791 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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