{"id":"GHSA-mx22-3794-2vpv","summary":"Excelize: Unchecked pivot-cache field index in extractPivotTableFields causes unrecoverable panic","details":"### Summary\n\nextractPivotTableFields builds `order := pc.getPivotCacheFieldsName()` from xl/pivotCache/pivotCacheDefinitionN.xml's \u003ccacheFields\u003e list, then indexes it with values taken from a *separately parsed* xl/pivotTables/pivotTableN.xml part with zero cross-validation: `order[field.Fld]` where `field.Fld` is a raw attacker-controlled `int` from the `\u003cdataField fld=\"N\"\u003e` attribute, and `order[fieldIdx]` where fieldIdx is a loop index over `pt.PivotFields.PivotField` that need not match the cache's field count. I executed two independent PoCs against the current HEAD: (1) trimmed the pivot cache's \u003ccacheFields\u003e to count=0 while leaving the pivot table's 2 pivotFields untouched -\u003e `runtime error: index out of range [0] with length 0` at pivotTable.go:1431; (2) left the 2 cache fields completely intact and only changed one attribute, `fld=\"1\"` -\u003e `fld=\"99999\"`, in xl/pivotTables/pivotTable1.xml -\u003e `runtime error: index out of range [99999] with length 2` at pivotTable.go:1443. Both stack traces confirmed via non-recovered `go test` runs: extractPivotTableFields -\u003e getPivotTable -\u003e GetPivotTables.\n\n### Reachability / who can trigger this\n\nUnauthenticated: any application that opens an untrusted .xlsx containing a pivot table and calls the public `File.GetPivotTables(sheet)` API. excelize has no recover() anywhere, so this crashes the host process (CLI/worker) or surfaces as an unhandled 500 in a request-scoped-recover HTTP service. Deterministic, single small crafted file, no user interaction beyond the service's normal open-and-read flow.\n\n### Proof of Concept / Reproduction\n\n**Method:**\n1) Verified source at HEAD (commit e81f0500, 2026-09-27, freshly cloned/up to date; `git status` clean except the new PoC files I added): read pivotTable.go:1425-1454 and confirmed verbatim: `order := pc.getPivotCacheFieldsName()` (1428), loop `for fieldIdx, field := range pt.PivotFields.PivotField` indexing `order[fieldIdx]` at axisRow/axisCol/axisPage (1431/1434/1437), and `Data: order[field.Fld]` (1443) inside the `pt.DataFields.DataField` loop -- zero bounds checks anywhere. Confirmed xmlPivotTable.go:271 `Fld int `xml:\"fld,attr\"`` on xlsxDataField (raw attacker-controlled int, no validation) and the sibling Fld field at line 252. Ran `go build ./...` -- compiles clean. Both citations are accurate.\n2) Found the repo already contained an untracked PoC test file from earlier work (pivot_fld_poc_test.go) implementing this exact finding via a byte-level zip-tamper technique (build a legitimate workbook with excelize's own public AddPivotTable API, then hex-edit one raw XML part inside the saved .xlsx's zip bytes -- not a hypothetical reimplementation, uses the real unmodified excelize package). Did not just trust it: ran it myself with `go test -run 'TestPivotTableDataFieldFldIndexPanic|TestPivotTableDataFieldFldAttributeOutOfRangePanic' -v .` and observed real PASS output with exact matching panic strings.\n3) For stronger, independent evidence beyond a recover-wrapped test, I wrote my own standalone non-test Go program from scratch, cmd/pivotcrash/main.go (module github.com/xuri/excelize/v2, go1.27.0 toolchain), that imports the real compiled excelize package (no reimplementation) with two subcommands: `gen`/`gen-trim` (attacker: build a legit pivot-table workbook via the public API, then rezip with one XML part tampered -- either dataField fld=\"1\"-\u003efld=\"99999\", or the pivot cache's \u003ccacheFields count=\"2\"\u003e collapsed to count=\"0\" -- writing the crafted .xlsx to disk) and `run` (victim: a fresh OS process that does exactly what any consumer service does -- `excelize.OpenFile(path)` then `f.GetPivotTables(\"Sheet1\")` -- with zero recover() anywhere in the file or the call chain). Executed as four separate `go run` process invocations: gen, run, gen-trim, run.\n\n**Evidence:**\nTest run (pre-existing PoC file, re-executed by me, both PASS):\n`--- PASS: TestPivotTableDataFieldFldIndexPanic (0.00s)` logging `CONFIRMED: GetPivotTables panicked ... runtime error: index out of range [0] with length 0`\n`--- PASS: TestPivotTableDataFieldFldAttributeOutOfRangePanic (0.00s)` logging `CONFIRMED: GetPivotTables panicked ... runtime error: index out of range [99999] with length 2`\n`ok  github.com/xuri/excelize/v2  0.114s`\n\nStandalone process-crash run #1 (`go run ./cmd/pivotcrash run pivotcrash_malicious.xlsx`, fld=\"99999\" tamper, cache untouched with 2 fields):\n[victim] file opened successfully, workbook parsed with no errors\n[victim] now calling f.GetPivotTables(\"Sheet1\") on the untrusted workbook...\npanic: runtime error: index out of range [99999] with length 2\ngoroutine 1 [running]:\ngithub.com/xuri/excelize/v2.(*File).extractPivotTableFields(...)\n\t.../pivotTable.go:1443 +0xb9b\ngithub.com/xuri/excelize/v2.(*File).getPivotTable(...)\n\t.../pivotTable.go:1379 +0x7f6\ngithub.com/xuri/excelize/v2.(*File).GetPivotTables(...)\n\t.../pivotTable.go:1278 +0x2f7\nmain.runVictim(...) / main.main() -\u003e exit status 2\n\nStandalone process-crash run #2 (`go run ./cmd/pivotcrash run pivotcrash_malicious_trim.xlsx`, cacheFields trimmed to count=0, pivot table's 2 pivotFields untouched):\npanic: runtime error: index out of range [0] with length 0\ngoroutine 1 [running]:\ngithub.com/xuri/excelize/v2.(*File).extractPivotTableFields(...)\n\t.../pivotTable.go:1431 +0xc15\ngithub.com/xuri/excelize/v2.(*File).getPivotTable(...)\n\t.../pivotTable.go:1379 +0x7f6\ngithub.com/xuri/excelize/v2.(*File).GetPivotTables(...)\n\t.../pivotTable.go:1278 +0x2f7\nmain.runVictim(...) / main.main() -\u003e exit status 2\n\nIn both standalone runs the \"GetPivotTables RETURNED NORMALLY\" print statement that follows the call was never reached -- the OS process itself terminated via an unrecovered Go panic (exit status 2), for a crafted .xlsx that `excelize.OpenFile` accepted without any error. Both stack traces terminate at the exact claimed sink lines (pivotTable.go:1443 and :1431) via the exact claimed call chain (extractPivotTableFields -\u003e getPivotTable -\u003e GetPivotTables). This is a real, unhandled crash of a real process running unmodified excelize code -- not a mock, not a simulated/hypothetical trace.\n\n### Novelty\n\nRan all 5 requested checks in full, plus extra verification. (1) Pulled the complete, paginated GHSA list via gh api (16 advisories, all state=published, no hidden drafts) and grepped full descriptions, not just summaries, for \"pivot\" -- only one incidental, non-overlapping hit (GHSA-wp2g-vpjj-g53r cites pivotTable.go:538 as an AddPivotTable call site for an unrelated formula-recursion stack-overflow bug). (2) Ran ~15 targeted GitHub issue searches (extractPivotTableFields, getPivotCacheFieldsName, GetPivotTables panic, dataField fld, BaseField, ShowValuesAs, \"index out of range\", cacheFields count mismatch, PivotFields panic, DataField, plus a broad \"pivot\" query returning 30 issues/PRs all individually triaged by title) and full-text-read the 5 most plausible (#2161, #1937, #2183, #1954, #1945) -- none match; the closest (#2161) is a nil-pointer bug in a different function/field, detailed above. (3) Checked PRs both by keyword (is:pr pivot = 10, is:pr \"pivotTable.go\" fld = 0, all reviewed; read PR #2168's full diff) and exhaustively (pulled all 31 currently-open PRs on the repo and reviewed every title) -- none touch pivot field indexing. (4) Ran 5 WebSearch queries combining the mechanism with \"excelize\"/\"pivot table\"/\"CVE\", and independently cross-checked OSV.dev's API (which mirrors NVD/GHSA/GO vuln DB) -- turned up only the already-ruled-out GHSA-fx5j (shared-string) and GHSA-h69g (row allocation) advisories, and a non-upstream automated \"task\"-tracking repo (windyswe/q\n...[truncated for brevity]\n\nClosest prior art considered: qax-os/excelize issue #2161 + merged PR #2168 (\"This closes #2161, fix panic on read unsupported pivot table cache source types\", merged 2025-07-05). That bug: pivotCacheDefinition.xml's \u003ccacheSource type=\"external\"/\u003e has no \u003cworksheetSource\u003e child, so pc.CacheSource.WorksheetSource is a nil pointer, and getPivotTable() (then pivotTable.go:875) dereferenced .Sheet/.Ref on it -\u003e nil-pointer-dereference panic, reached via GetPivotTables (then line 803). Fix was an early type-validation error return in getPivotTable, not any bounds check. SAME-FIX TEST: would that fix also close the candidate bug? No. The candidate's panic is index-out-of-range (not nil-deref) inside a different function, extractPivotTableFields, on a different data structure: `order := pc.getPivotCacheFieldsName()` (length = count of \u003ccacheFields\u003e) indexed by (a) a loop counter over pt.PivotFields.PivotField (a separate, unrelated count from pivotTableN.xml) at lines 1431/1434/1437, and (b) the raw unvalidated int field.\n...[truncated for brevity]\n\n### Independent skeptical review\n\nTried hard to kill this and it holds. Independently re-read current HEAD (e81f05008b3, fetched and diffed against origin/master to confirm it's current) rather than trusting the report: pivotTable.go:1427-1454 (extractPivotTableFields) has zero bounds checks on order[fieldIdx] (axisRow/Col/Page branches, lines 1431/1434/1437) or order[field.Fld] (line 1443) — confirmed by direct Read, matching the claim's line citations exactly. This is a genuine oversight, not a designed invariant: the very next function in the same file, extractPivotTableShowValuesAs (lines 1476, 1486) and extractPivotTableField (line 1508), DO bounds-check structurally identical order/slice indices before using them — the developers clearly know this pattern needs guarding and simply missed it in extractPivotTableFields. Confirmed xmlPivotTable.go:271 Fld is a bare unchecked `int` XML attribute, and confirmed getPivotTable/pivotCacheReader/pivotTableReader perform no count-vs-actual-length cross-validation between the independently-parsed pivotTable and pivotCache XML parts. Grepped the entire repo for recover() — zero hits outside the researcher's own test file, confirming \"no recover anywhere\" is accurate. Re-ran both provided PoCs myself in a throwaway test file against this exact HEAD (go test -run TestPoC_PivotCache -v): both panic exactly as claimed, with byte-identical messages — \"index out of range [0] with length 0\" (truncated-cache-fields PoC, line 1431) and \"index out of range [99999] with lengt\n...[truncated for brevity]","aliases":["CVE-2026-107211"],"modified":"2026-10-08T18:00:09.701961422Z","published":"2026-10-08T17:52:17Z","database_specific":{"github_reviewed_at":"2026-10-08T17:52:17Z","nvd_published_at":"2026-10-07T18:17:18Z","cwe_ids":["CWE-129"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/qax-os/excelize/security/advisories/GHSA-mx22-3794-2vpv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107211"},{"type":"WEB","url":"https://github.com/qax-os/excelize/pull/2435"},{"type":"WEB","url":"https://github.com/qax-os/excelize/commit/6258dcebc4e2a2aed985c38a08098dfd908521d1"},{"type":"PACKAGE","url":"https://github.com/qax-os/excelize"}],"affected":[{"package":{"name":"github.com/xuri/excelize/v2","ecosystem":"Go","purl":"pkg:golang/github.com/xuri/excelize/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.8.1"},{"fixed":"2.11.1-0.20261003002531-6258dcebc4e2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-mx22-3794-2vpv/GHSA-mx22-3794-2vpv.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}