CVE-2026-70453Network attack vector

CPU exhaustion via equal-checksum hash chains

Published Aug 13, 2026 · Updated Aug 13, 2026

Algorithmic complexity in rsync's hash_search() before 3.5.0 allows remote attackers to exhaust sender CPU with crafted checksum sets. A receiver-supplied checksum set with a long chain of equal weak checksums makes hash_search() repeat match verification at each sender offset, producing quadratic work. An unauthenticated peer that controls the receiver side of a transfer can pin one CPU core on the shared sender host without ending its own connection.

CVSS severity8.7
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithmic complexity in rsync's hash_search() before 3.5.0 allows remote attackers to exhaust sender CPU with crafted checksum sets. A receiver-supplied checksum set with a long chain of equal weak checksums makes hash_search() repeat match verification at each sender offset, producing quadratic work. An unauthenticated peer that controls the receiver side of a transfer can pin one CPU core on the shared sender host without ending its own connection.

The record

CVE
CVE-2026-70453
Published
Aug 13, 2026
Updated
Aug 13, 2026
Vendor
Rsync Project
Product
rsync
Classifications
CWE-407, T1499.003
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

8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5Rsync ProjectCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-407Inefficient Algorithmic Complexity
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

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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