CVE-2026-59162: Excelize Negative Shared-string Index Causes Panic Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fx5j-qcqg-grpf",
  "modified" : "2026-09-10T15:08:53Z",
  "published" : "2026-09-10T15:08:53Z",
  "aliases" : [ "CVE-2026-59162" ],
  "summary" : "Excelize: Negative shared-string index causes panic in GetCellValue and GetRows",
  "details" : "# Negative shared-string index causes panic in GetCellValue and GetRows\n\n## Summary\n\nExcelize 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 `<v>-1</v>`, the parsed index is negative. The upper-bound check still passes (`len(sharedStrings) > -1`), and Excelize indexes `sharedStrings[-1]`, causing a runtime panic.\n\nThis was reproduced on the current default branch commit `1213a8bd7c5ab360554603ac5c995ccaf6eb4314` and the latest release tag `v2.10.1` (`5ad5ab3af0054c55bdce09f1530085600e9f2e45`). The issue is independent from the row-bound allocation report, so I am reporting it separately.\n\n## Affected package\n\n- Package: `github.com/xuri/excelize/v2`\n- Tested affected versions: current default branch at `1213a8bd7c5ab360554603ac5c995ccaf6eb4314`, and release `v2.10.1`\n- Fixed version: none known at the time of this report\n\n## Impact\n\nAn 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.\n\n## Root cause\n\nFor 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:\n\n```go\nxlsxSI, _ := strconv.Atoi(strings.TrimSpace(c.V))\nif len(d.SI) > xlsxSI {\n    return d.SI[xlsxSI].String(), nil\n}\n```\n\nFor `xlsxSI == -1`, `len(d.SI) > -1` is true, so the code proceeds to index `d.SI[-1]` and panics.\n\n## Minimal worksheet payload\n\n```xml\n<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<worksheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\">\n  <sheetData>\n    <row r=\"1\"><c r=\"A1\" t=\"s\"><v>-1</v></c></row>\n  </sheetData>\n</worksheet>\n```\n\nThe workbook also contains a normal `sharedStrings.xml` with one string (`ok`), so the failure is specifically due to accepting a negative index.\n\n## Reproduction\n\nCalling `GetCellValue(\"Sheet1\", \"A1\")` on the workbook panics:\n\n```text\n== negative shared string GetCellValue ==\nelapsed=0s alloc_delta=0MB\nPANIC: runtime.boundsError runtime error: index out of range [-1]\n```\n\nCalling `GetRows(\"Sheet1\")` on the same workbook also panics:\n\n```text\n== negative shared string GetRows ==\nelapsed=0s alloc_delta=0MB\nPANIC: runtime.boundsError runtime error: index out of range [-1]\n```\n\nThe same results were observed on current default branch commit `1213a8bd7c5ab360554603ac5c995ccaf6eb4314` and on release `v2.10.1`.\n\n## Expected behavior\n\nMalformed shared-string indices should be rejected or treated as missing/invalid string references without panicking.\n\n## Suggested remediation\n\nCheck both lower and upper bounds before indexing the shared string table. For example:\n\n```go\nif xlsxSI >= 0 && xlsxSI < len(d.SI) {\n    return d.SI[xlsxSI].String(), nil\n}\n```\n\nAdd regression tests for `GetCellValue()` and `GetRows()` on `t=\"s\"` cells whose `<v>` value is negative.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/xuri/excelize/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.11.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/xuri/excelize"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/qax-os/excelize/security/advisories/GHSA-fx5j-qcqg-grpf"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59162"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/qax-os/excelize/pull/2331"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/qax-os/excelize/commit/93f0b3caed37f21ef5079e3259c6c21dcfe68453"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/qax-os/excelize"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/qax-os/excelize/releases/tag/v2.11.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248", "CWE-755" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-10T15:08:53Z",
    "nvd_published_at" : "2026-07-10T17:17:02Z"
  }
}