CVE-2026-53791Network attack vectorHinoki check available

IP-based access-control bypass via untrusted PROXY headers

Published Aug 13, 2026 · Updated Aug 13, 2026

Authentication bypass in rsync daemon before 3.5.0 allows remote attackers to evade IP-based access controls using forged PROXY headers. The daemon trusts the header's forwarded source address without verifying that the direct peer is an authorized proxy, then evaluates hosts allow/deny against the forged address. Exposure requires the non-default proxy protocol setting, a directly reachable daemon port, and IP-based module restrictions; successful spoofing grants access those rules should block.

CVSS severity9.1
Critical
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authentication bypass in rsync daemon before 3.5.0 allows remote attackers to evade IP-based access controls using forged PROXY headers. The daemon trusts the header's forwarded source address without verifying that the direct peer is an authorized proxy, then evaluates hosts allow/deny against the forged address. Exposure requires the non-default proxy protocol setting, a directly reachable daemon port, and IP-based module restrictions; successful spoofing grants access those rules should block.

The record

CVE
CVE-2026-53791
Published
Aug 13, 2026
Updated
Aug 13, 2026
Vendor
Rsync Project
Product
rsync
Classifications
CWE-290, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=3.4.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rsync Project · rsyncversion=0 <=3.4.4

Published CVSS scores

9.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
9.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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