CVE-2026-78206

Summary

exceljs-hardened before 5.0.0 decompresses all entries from supplied xlsx archives into memory without limits on entry size, total size, or compression ratio. Attackers can upload highly compressed workbooks that expand to gigabytes in memory, exhausting available resources and causing denial of service.

Affected Software

Weaknesses

• CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)

References

• https://github.com/exceljs/exceljs
• https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-7cvf-3r55-r39q
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/xlsx/xlsx.js#L257-L281
• https://www.vulncheck.com/advisories/exceljs-through-uncontrolled-resource-consumption-via-unbounded-xlsx-decompression

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