CVE-2026-78206Network attack vector

Service crash via unbounded XLSX decompression

Published Aug 24, 2026 · Updated Aug 24, 2026

Uncontrolled resource consumption in ExcelJS 4.4.0 and earlier allows remote attackers to crash services through crafted XLSX files. Workbook.xlsx.load() calls JSZip.loadAsync(), then converts each archive entry entirely to a buffer or string without entry, aggregate, or compression-ratio limits. Reachability requires an application to pass an attacker-supplied workbook to load() or readFile(); expansion can exhaust memory and terminate the hosting process.

CVSS severity8.7
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in ExcelJS 4.4.0 and earlier allows remote attackers to crash services through crafted XLSX files. Workbook.xlsx.load() calls JSZip.loadAsync(), then converts each archive entry entirely to a buffer or string without entry, aggregate, or compression-ratio limits. Reachability requires an application to pass an attacker-supplied workbook to load() or readFile(); expansion can exhaust memory and terminate the hosting process.

The record

CVE
CVE-2026-78206
Published
Aug 24, 2026
Updated
Aug 24, 2026
Vendor
ExcelJS
Product
ExcelJS
Classifications
CWE-409, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 24, 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 <=4.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ExcelJS · ExcelJSversion=0 <=4.4.0

Published CVSS scores

7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-409Improper Handling of Highly Compressed Data (Data Amplification)
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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