CVE-2026-59933Public exploitNetwork attack vector

Service interruption via cyclic OLE sector chain

Published Jul 28, 2026 · Updated Jul 28, 2026

Uncontrolled resource consumption in PHPOffice PhpSpreadsheet allows remote attackers to crash PHP workers with malformed XLS files. The OLERead::read() small-block depot loop trusts XLS/OLE sector links, tracks neither visited sectors nor a chain limit, and repeatedly appends a self-referencing sector until PHP exhausts memory. Affected releases are before 1.30.6, 2.0.0 through 2.1.17, 2.2.0 through 2.4.6, 3.3.0 through 3.10.6, and 4.0.0 through 5.8.0; upload-processing applications expose their PHP workers to a service-interrupting crash.

CVSS severity7.5
High
EPSS probability0.38%
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 PHPOffice PhpSpreadsheet allows remote attackers to crash PHP workers with malformed XLS files. The OLERead::read() small-block depot loop trusts XLS/OLE sector links, tracks neither visited sectors nor a chain limit, and repeatedly appends a self-referencing sector until PHP exhausts memory. Affected releases are before 1.30.6, 2.0.0 through 2.1.17, 2.2.0 through 2.4.6, 3.3.0 through 3.10.6, and 4.0.0 through 5.8.0; upload-processing applications expose their PHP workers to a service-interrupting crash.

The record

CVE
CVE-2026-59933
Published
Jul 28, 2026
Updated
Jul 28, 2026
Vendor
PHPOffice
Product
PhpSpreadsheet
Classifications
CWE-400, CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 1.30.6
  2. Affected versionversion=>= 2.0.0, < 2.1.18
  3. Affected versionversion=>= 2.2.0, < 2.4.7
  4. Affected versionversion=>= 3.3.0, < 3.10.7
  5. Affected versionversion=>= 4.0.0, < 5.8.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PHPOffice · PhpSpreadsheetversion=< 1.30.6; version=>= 2.0.0, < 2.1.18; version=>= 2.2.0, < 2.4.7; version=>= 3.3.0, < 3.10.7; version=>= 4.0.0, < 5.8.1

Published CVSS scores

7.5GitHub, Inc.CVSS: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 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 exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

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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