Excelize: A Zip64 uncompressed-size of 2^63 panics OpenFile/OpenReader

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.1.0 to 2.11.0, a Zip64 uncompressed size with the high bit set is converted from uint64 to a negative int64 before signed size-limit checks and allocation. ReadZipReader obtains UncompressedSize64 through FileInfo.Size and passes the wrapped negative value to readFile. When a crafted Zip64 entry declares an uncompressed size from 2^63 through 2^64-1 and the workbook is opened, the negative size bypasses unzip limits and reaches make as a negative capacity, allowing an attacker to panic during workbook opening. No fixed version is available as of this review.

Source published

7 Oct 2026 18:53:27 UTC

Source modified

7 Oct 2026 19:30:13 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H