CVE-2026-72792 — kernel

CVE: This vulnerability corresponds to CVE-2026-72792.

Summary

/api/tag/getTag filters its results for reader roles through FilterTagsByPublishIgnore, which checks only the visible publish tier. Documents that are published but password-protected pass that check, so a reader who has never entered a document's publish password receives every tag label used inside it, together with occurrence counts.

The project has already treated this exact tier mismatch as a vulnerability on a sibling path: commit 82e9ded42 ("Enforce publish access for graph nodes") moved the graph endpoint off the visible-only filter and onto a password-aware one. FilterTagsByPublishIgnore was not upgraded alongside it.

Details

The tier mismatch. For reader roles, getTag filters via:

publishIgnore := GetInvisiblePublishAccess(publishAccess)
tags = FilterTagsByPublishIgnore(publishIgnore, tags)

FilterTagsByPublishIgnore counts a label if CheckPathAccessableByPublishIgnore(span.Box, span.Path, publishIgnore) holds, then reads label := util.UnescapeHTML(span.Content).

CheckPathAccessableByPublishIgnore (kernel/model/publish_access.go:183) consults the invisible set only. It returns true for any visible document, including one carrying a publish password. The project's complete gate is checkBlockTreeAccessableByPublishAccess (kernel/model/publish_access.go:225), which ANDs that same visibility test with password == "" || CheckPublishAuthCookie(...). The tag filter implements the first half and omits the second.

The disclosed value is user-authored content, not a structural identifier: span.Content is the tag text an author wrote inside the document project codenames, personal names, client names, subject matter and the accompanying count reveals how heavily each appears.

Established as a defect by the project's own remediation. Commit 82e9ded42 replaced the graph endpoint's visible-only FilterGraphByPublishIgnore with a filter that additionally resolves the document's publish password and validates CheckPublishAuthCookie. The reasoning that motivated that change applies unchanged here: same input shape, same visible-only body, same class of leaked material. FilterTagsByPublishIgnore retains the pre-fix pattern.

Verified unfixed. At v3.7.4-alpha.1, getTag still calls FilterTagsByPublishIgnore, and that function's body still tests only CheckPathAccessableByPublishIgnore. No commit on the development branch touches kernel/api/tag.go or the tag filter (git log and git log -S both empty over that range).

Scope note on the remaining visible-only call sites. Two further consumers of the *ByPublishIgnore tier were reviewed and are not claimed as vulnerabilities in this report: listDocsByPath (kernel/model/filetree.go:1160), which exposes document titles and is plausibly intentional for navigation, and the identifier-only filter, which returns no authored content. They are noted because the visible-only tier is now a repeated source of defects, and an audit of every *ByPublishIgnore call site is the durable remedy rather than a third individual patch.

Proof of Concept

Precondition: publish mode enabled (default port 6808); a published document that carries a publish password and contains at least one tag; a reader session that has not authenticated to that document.

POST http://127.0.0.1:6808/api/tag/getTag
{}

→ 200
   The returned tag tree includes labels sourced from the password-protected
   document, with counts, despite the session holding no publish auth cookie
   for it.

Differential check: request the document itself through a password-gated endpoint with the same session and observe that access is refused, while its tag labels remain present in the getTag response.

Impact

An anonymous reader in publish mode or any publish RoleReader enumerates the tag vocabulary of documents they are not authorized to open, along with usage counts. Tags are author-written free text, so this discloses subject matter, names and internal terminology from documents whose contents the publish password was configured to protect. Confidentiality-only.

Suggested fix

Replace FilterTagsByPublishIgnore with a password-aware filter mirroring the one introduced in 82e9ded42 for graph nodes: resolve each span's document password via GetPathPasswordByPublishAccess and require CheckPublishAuthCookie before the label is counted, in addition to the existing visibility test. More durably, audit every remaining *ByPublishIgnore call site against checkBlockTreeAccessableByPublishAccess the visible-only tier has now produced this defect on at least two separate endpoints.