COMPOSER · JUNE 2026 · EARLY WARNING

PHPSpreadsheet Patch Bypass Under Investigation

EARLY WARNING · UNCONFIRMED. This page describes a developing threat that 0Day surfaced from early signals and has not yet independently confirmed. Details may change. Always verify against the primary sources before acting.

CVE-2026-34084GHSA-87M4-826X-3CRXSeverity: HIGH

An early warning indicates that PHPSpreadsheet may have a bypass for the CVE-2026-34084 patch, potentially allowing remote code execution. Users of the phpspreadsheet package are advised to take precautions.

What happened

Reportedly, the PHPSpreadsheet package has a bypass for the patch of CVE-2026-34084, which could enable remote code execution under certain conditions. This issue is currently under investigation and has been tracked with the IDs CVE-2026-34084 and GHSA-87M4-826X-3CRX. To assess your exposure, check if your project utilizes the phpspreadsheet package via composer. It is recommended to upgrade to the latest version of phpspreadsheet and ensure that no phar wrappers are used in file paths. For more detailed information, consult the primary sources.

How 0Day mitigates this

MATCHED TO YOUR ACTUAL DEPENDENCY GRAPH0Day matches every incoming threat signal against your GitHub organization’s full dependency graph, including transitive dependencies. If phpspreadsheet is anywhere in your dependency tree, the engineers who own the affected repositories get a push alert the moment it is flagged — no manual audit to remember to run.

Read how this differs from waiting on a scanner to catch a known advisory, or see the exact, read-only access 0Day needs to do this for an organization.

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