{"id":"CVE-2026-39377","aliases":["GHSA-4c99-qj7h-p3vg","PYSEC-2026-2229"],"url":"https://o3.security/vulnerability/CVE-2026-39377","summary":"nbconvert has an Arbitrary File Write via Path Traversal in Cell Attachment Filenames","details":"# Arbitrary File Write via Path Traversal in Cell Attachment Filenames\n\n## Summary\n\nnbconvert allows arbitrary file writes to locations outside the intended output directory when processing notebooks containing crafted cell attachment filenames. The `ExtractAttachmentsPreprocessor` passes attachment filenames directly to the filesystem without sanitization, enabling path traversal attacks. This vulnerability provides complete control over both the destination path and file extension.\n\n\n## Impact\n\nThis vulnerability allows writing files with arbitrary content to arbitrary filesystem locations, limited only by the permissions of the process running nbconvert. The attacker controls:\n- Full destination path (via `../` traversal)\n- Filename\n- File extension\n- File content\n\n## Patches\n\n- upgrade to nbconvert v7.17.1\n\n## Workarounds\n\ndisable ExtractAttachmentsPreprocessor by setting:\n\n```python\nc. ExtractAttachmentsPreprocessor.enabled = False\n```","published":"2026-04-21T00:14:59.937Z","modified":"2026-10-28T02:30:44.986011454Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"},"epss":{"score":0.00266,"percentile":0.18504,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"nbconvert","fixedVersion":"7.17.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/jupyter/nbconvert/releases/tag/v7.17.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39377.json"},{"type":"ADVISORY","url":"https://github.com/jupyter/nbconvert/security/advisories/GHSA-4c99-qj7h-p3vg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39377"},{"type":"PACKAGE","url":"https://github.com/jupyter/nbconvert"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:44.986011454Z"}}