PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustion

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-59933: 0.46% estimated exploitation activity in the next 30 days; percentile 40.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary PhpSpreadsheet's OLE reader follows sector chains from attacker-controlled XLS/OLE metadata without detecting cycles or enforcing a maximum chain length. A tiny malformed .xls/OLE file can set the small-block depot sector chain to point back to itself. During normal XLS detection, OLERead::read() appends the same sector data repeatedly until the PHP process exhausts memory. This is reachable from Reader\Xls::canRead() and therefore from automatic spreadsheet type detection. Applications that accept attacker-controlled spreadsheet uploads can suffer denial of service from a very small file. Vulnerability details OLERead::read() loads the input and builds sector chains from attacker-controlled OLE header and allocation-table values: - src/PhpSpreadsheet/Shared/OLERead.php:82 reads the entire file after validating only the OLE magic. - src/PhpSpreadsheet/Shared/OLERead.php:84-97 reads sector-chain metadata from the file header. - src/PhpSpreadsheet/Shared/OLERead.php:132-146…

Published by the source

23 Jul 2026, 15:01 UTC

Last modified by the source

23 Jul 2026, 15:01 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xh5m-36r6-47m3

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-59933

Advisory: PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustion
IDs: CVE-2026-59933, GHSA-xh5m-36r6-47m3
Record: https://patchnext.com/advisories/cve-2026-59933 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: phpoffice/phpspreadsheet 5.8.1, 3.10.7, 2.4.7, 2.1.18, 1.30.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist phpoffice/phpspreadsheet: affected >= 4.0.0, <= 5.8.0; >= 3.3.0, <= 3.10.6; >= 2.2.0, <= 2.4.6; >= 2.0.0, <= 2.1.17; <= 1.30.5; fixed in 2.1.18, 3.10.7, 2.4.7, 1.30.6, 5.8.1

## Suggested inspection (read-only)
- Packagist phpoffice/phpspreadsheet: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on phpoffice/phpspreadsheet.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xh5m-36r6-47m3 (GitHub-reviewed advisory GHSA-xh5m-36r6-47m3 lists affected ranges: Packagist phpoffice/phpspreadsheet >=4.0.0 =3.3.0 =2.2.0 =2.0.0 =0 <=1.30.5)

Commands are suggestions: review each one before running it.