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EUVD-2026-356479

fkie_cve-2026-44829

Gotenberg is a Docker-powered stateless API for PDF files. In 8.32.0 and earlier, filename handling in pkg/modules/api/context.go uses filepath.Base on Linux, which does not treat backslashes as path separators, so a multipart filename containing Windows-style parent directory components survives sanitization. The original filename flows through ctx.diskToOriginal and the multi-output PDF routes into archives.FilesFromDisk and archives.Zip.Archive as the generated zip entry name. A remote attacker can submit a name such as ........\Windows\System32\evil.pdf through an upload or an upstream downloadFrom Content-Disposition header, and a Windows archive extractor can write the resulting file outside the intended extraction directory. The affected paths include /forms/pdfengines/split and other multi-output PDF, LibreOffice, and conversion routes, and exploitation can cause arbitrary file writes on a downstream Windows system when a user or process extracts the returned archive. This issue is fixed in version 8.33.0.

GHSA-hwc4-gmrw-5222 — Gotenberg has path traversal in zip entry name via Windows-style separators in upload filename

Affected: Go: github.com/gotenberg/gotenberg/v8

### Summary `filepath.Base` on the Linux container does not strip backslashes (`\`), because `\` is only a path separator on Windows. A multipart filename like `..\..\..\..\Windows\System32\evil.pdf` survives Gotenberg's input sanitisation and lands verbatim as the zip entry name when a multi-output route returns its result as a zip (e.g. `/forms/pdfengines/split`). Windows zip extractors interpret `\` as a path separator and write the file outside the extraction directory.

### Details `pkg/modules/api/context.go:434, 472`: ```go filename := norm.NFC.String(filepath.Base(fh.Filename)) ``` On Linux, `filepath.Base("..\\..\\..\\..\\Windows\\System32\\evil.pdf")` returns the same string verbatim — there are no `/` separators to find. The original filename then flows to `ctx.diskToOriginal` (`pkg/modules/api/context.go:459, 393`) and through `pkg/modules/pdfengines/routes.go:287-322` (`SplitPdfStub`), which builds: ```go originalNameNoExt := strings.TrimSuffix(originalName, filepath.Ext(originalName)) newOriginal := fmt.Sprintf("%s_%d.pdf", originalNameNoExt, i) ctx.RegisterDiskPath(newPath, newOriginal) ``` Finally `pkg/modules/api/context.go:617-642` constructs the zip via `archives.FilesFromDisk` + `archives.Zip{}.Archive`. `mholt/archives@v0.1.5/archives.go:155-184` (`nameOnDiskToNameInArchive`) returns `path.Join(rootInArchive, "")` — the map value verbatim.

### Suggested fix ```diff - filename := norm.NFC.String(filepath.Base(fh.Filename)) + filename := sanitizeFile…