CVE-2026-72805

**CVE:** This vulnerability corresponds to [CVE-2026-72805](https://nvd.nist.gov/vuln/detail/CVE-2026-72805). ### Summary Three block endpoints return document content snippets and metadata without any publish-access check, while their sibling `getBlockInfo` which returns comparable data does enforce one. All three are `CheckAuth`-only, so they are reachable by the publish `RoleReader` token and by the anonymous account when `Publish.Auth.Enable` is `false`. An anonymous reader supplying a block ID receives content and metadata belonging to publish-forbidden and password-protected documents. ### Details `getBlockInfo` (`kernel/api/block.go`) gates on the publish boundary: ```go if !checkBlockPublishAccess(c, id, ret) { return } ``` The following siblings in the same file perform no equivalent check: | Endpoint | Returns | Publish check | |---|---|---| | `getBlockInfo` | root/title/path metadata | `checkBlockPublishAccess`: present | | `getBlockBreadcrumb` | `BlockPath.Name` : root document title plus every ancestor block's content snippet | none | | `getRefText` | the block's reference/anchor text (document content) | none | | `getBlockTreeInfos` | root/title/path metadata for arbitrary block IDs | none | `getBlockBreadcrumb` returns the full ancestor chain including each ancestor block's content snippet, and `getRefText` returns block anchor text both are document content, not just metadata. `getBlockTreeInfos` returns root/title/path for any caller-supplied ID set via `model.GetBlockTreeInfosInBox(...)` with no gate. `getBlockBreadcrumb` and `getRefText` additionally accept a client-supplied notebook argument that routes to the `*InBox` variants, so the same unguarded path applies to encrypted-notebook reads while the notebook is unlocked. The correct primitive already exists in the codebase and is used by `getBlockInfo`; these three handlers simply do not call it. ### Proof of Concept Precondition: publish mode enabled (default port 6808); anonymous when `Publish.Auth.Enable` is `false`, otherwise any publish reader account. A document `D` is marked publish-forbidden (or password-protected) and contains a block `BLOCK_ID` under a heading with distinctive content. **Control: the gated sibling correctly refuses:** ``` POST http://127.0.0.1:6808/api/block/getBlockInfo {"id":"BLOCK_ID"} ``` Blocked by `checkBlockPublishAccess`. **Disclosure: the ungated siblings return the data anyway:** ``` POST http://127.0.0.1:6808/api/block/getBlockBreadcrumb {"id":"BLOCK_ID"} → ancestor chain including the forbidden document's title and ancestor block content snippets POST http://127.0.0.1:6808/api/block/getRefText {"id":"BLOCK_ID"} → the block's reference/anchor text (content of the forbidden document) POST http://127.0.0.1:6808/api/block/getBlockTreeInfos {"ids":["BLOCK_ID"]} → root ID, title, and path for the forbidden document ``` Verified by code inspection at `origin/master` (`eef10568`): `getBlockInfo` contains the `checkBlockPublishAccess` call; `getBlockBreadcrumb`, `getRefText`, and `getBlockTreeInfos` contain no publish-access, publish-ignore, or readonly-role check in their bodies. ### Impact An anonymous reader (publish mode with auth disabled) or any publish `RoleReader` can read, for documents explicitly excluded from publishing or protected by a publish password: - the document title and full ancestor chain, including ancestor block content snippets (`getBlockBreadcrumb`); - block reference/anchor text, i.e. document content (`getRefText`); - root ID, title, and path metadata for arbitrary block IDs (`getBlockTreeInfos`). Because `getBlockBreadcrumb` and `getRefText` accept a notebook argument routing to the `*InBox` variants, the same disclosure applies to encrypted notebooks while unlocked. Confidentiality-only; the precondition is a block ID, obtainable from other reader-reachable endpoints. ### Suggested fix Call `checkBlockPublishAccess` (as `getBlockInfo` does) in `getBlockBreadcrumb`, `getRefText`, and `getBlockTreeInfos` before returning data for `getBlockTreeInfos`, apply it per ID and drop unauthorized entries. Confirm the `*InBox` variants (`GetBlockRefTextInBox`, `BuildBlockBreadcrumbInBox`) enforce the same boundary so the notebook-argument path is covered.

No confirmed active exploitation of CVE-2026-72805 has been reported, but organizations should still patch proactively.

Update to patched version: Jupyter Notebook 0.0.0-20260723163028-931ba693375e.

CVE-2026-72805 has a CVSS v3.1 base score of 5.8 (MEDIUM). The EPSS exploitation probability is 0.24%.