Is excelize:excelize safe?

CVE-2026-59162

Excelize parses shared-string cell values with strconv.Atoi and checks only the upper bound before indexing the shared string slice. If an XLSX file contains a shared-string cell with -1, the parsed index is negative. The upper-bound check still passes (len(sharedStrings) > -1), and Excelize indexes sharedStrings[-1], causing a runtime panic.

This was reproduced on the current default branch commit 1213a8bd7c5a and the latest release tag v2.10.1 (5ad5ab3af005). The issue is independent from the row-bound allocation report, so I am reporting it separately.

• Package: github.com/xuri/excelize/v2
• Tested affected versions: current default branch at 1213a8bd7c5a, and release v2.10.1
• Fixed version: none known at the time of this report

An attacker who can provide an XLSX file to an application using Excelize can trigger a process panic when the application reads the malicious cell through common APIs such as GetCellValue or GetRows. In services that parse untrusted spreadsheets without a panic recovery boundary, this can cause denial of service.

For shared-string cells (t="s"), xlsxC.getValueFrom() parses the cell value as a shared-string index and only checks whether the index is below len(d.SI) before indexing:

xlsxSI, _ := strconv.Atoi(strings.TrimSpace(c.V))
if len(d.SI) > xlsxSI {
    return d.SI[xlsxSI].String(), nil
}

For xlsxSI == -1, len(d.SI) > -1 is true, so the code proceeds to index d.SI[-1] and panics.

  
    -1
  

The workbook also contains a normal sharedStrings.xml with one string (ok), so the failure is specifically due to accepting a negative index.

Calling GetCellValue("Sheet1", "A1") on the workbook panics:

== negative shared string GetCellValue ==
elapsed=0s alloc_delta=0MB
PANIC: runtime.boundsError runtime error: index out of range [-1]

Calling GetRows("Sheet1") on the same workbook also panics:

== negative shared string GetRows ==
elapsed=0s alloc_delta=0MB
PANIC: runtime.boundsError runtime error: index out of range [-1]

The same results were observed on current default branch commit 1213a8bd7c5a and on release v2.10.1.

Malformed shared-string indices should be rejected or treated as missing/invalid string references without panicking.

Check both lower and upper bounds before indexing the shared string table. For example:

if xlsxSI >= 0 && xlsxSI ` value is negative.