CVE-2026-82651 — kernel

Summary

GHSA-c8r8-95hg-mp34 added a centralized guard, util.IsForbiddenAbsPath(), specifically to block access to a small set of sensitive files: conf/conf.json (plaintext accessAuthCode/API token/cookie key), data/snippets/conf.json, the entire data/templates/ directory, and data/.siyuan/publishAccess.json (plaintext publish-mode passwords). It was applied to kernel/api/file.go and kernel/mcp/tools/file.go. Two other routes in the same server that serve arbitrary files by path, /history/*path and /repo/diff/*path, construct their target paths independently and were not updated to call this new guard. Since the repo/history snapshot system's tracked root is data/ (confirmed by getSyncIgnoreLines(), whose ignore file lives at data/.siyuan/syncignore with entries relative to data/), both data/.siyuan/publishAccess.json and data/templates/* fall within the scope that can legitimately be captured in historical snapshots, meaning a prior version of either file can exist in util.HistoryDir/the repo-diff temp checkout even after the live file has been protected by the new guard. This is CWE-862 (Missing Authorization) applied to a very recently introduced protection mechanism.

Details

kernel/server/serve.go, /history/*path (around line 994):

ginServer.GET("/history/*path", model.CheckAuth, model.CheckAdminRole, func(context *gin.Context) {
    p := filepath.Join(util.HistoryDir, context.Param("path"))
    // 加密笔记本的历史是密文（.sy/assets/AV），需先解密再输出
    if serveEncryptedHistory(context, p) {
        return
    }
    secureAssetContentHeaders(context, p, p)
    http.ServeFile(context.Writer, context.Request, p)
})

No call to util.IsForbiddenAbsPath(p) anywhere in this handler.

kernel/server/serve.go, /repo/diff/*path (around line 1241):

ginServer.GET("/repo/diff/*path", model.CheckAuth, model.CheckAdminRole, func(context *gin.Context) {
    requestPath := filepath.Clean(context.Param("path"))
    if strings.Contains(requestPath, "..") {
        context.Status(http.StatusUnauthorized)
        return
    }
    ...
    p := filepath.Join(repoDiffBaseDir, requestPath)
    if !gulu.File.IsSubPath(repoDiffBaseDir, p) {
        context.Status(http.StatusUnauthorized)
        return
    }
    http.ServeFile(context.Writer, context.Request, p)
})

This route does have its own traversal protection (.. rejection and IsSubPath containment within repoDiffBaseDir), but that only prevents escaping the diff-checkout directory, it does nothing to prevent retrieving a legitimately checked-out historical copy of publishAccess.json or a templates file from within that directory, which is exactly what the new guard exists to prevent regardless of which directory the copy currently sits in.

util.IsForbiddenAbsPath() itself (kernel/util/path_guard.go, introduced by the referenced fix) confirms the intended scope:

// 禁止访问 data/.siyuan/publishAccess.json（含发布模式明文访问密码）
publishAccessPath := NormalizeAndResolve(filepath.Join(DataDir, ".siyuan", "publishAccess.json"))
if fileNorm == publishAccessPath {
    return true
}

and

// 禁止访问 data/templates 目录（含目录本身及其全部子路径）
templatesBase := NormalizeAndResolve(filepath.Join(DataDir, "templates"))
if fileNorm == templatesBase || gulu.File.IsSubPath(templatesBase, fileNorm) {
    return true
}

Both are paths within data/, the same root the sync/history/repo system tracks.

Step-by-step reproduction

1. As the workspace admin, enable Publish with a password on at least one notebook (creating data/.siyuan/publishAccess.json with a plaintext password), then let a sync/backup snapshot capture this state (or check whether local history capture already covers data/.siyuan/ in the deployed version).
2. Change or remove the publish password, so the live publishAccess.json no longer contains the old plaintext password the new guard is meant to hide, going forward.
3. As the admin, request the historical/diff version instead of the live file:

   curl -s http://<target>:6806/history/<snapshot-path-to-publishAccess.json> \
     -u "<workspaceName>:<accessAuthCode>"
   curl -s http://<target>:6806/repo/diff/<diff-path-to-publishAccess.json> \
     -u "<workspaceName>:<accessAuthCode>"
   

4. Expected if consistently protected, matching the behavior the new guard already provides on the live-file endpoints: rejected. Observed: neither handler calls IsForbiddenAbsPath, so the historical copy is served if it exists in that location.

(Not run against a live compiled kernel, same sandbox limitation noted throughout this review; both handlers are read directly from source at the reviewed commit, and IsForbiddenAbsPath's scope, plus the sync-root confirmation via getSyncIgnoreLines(), are quoted directly above. Whether these specific files are captured by history/repo snapshots in a given deployment depends on the workspace's actual usage history and was not independently verified against a live instance in this review.)

Impact

An admin-authenticated request to either route can potentially retrieve a historical copy of data/.siyuan/publishAccess.json (disclosing a plaintext publish-mode password even after it has been changed or the live file has been protected) or a data/templates/* file, directly undermining the protection GHSA-c8r8-95hg-mp34 was written four days prior to this review specifically to provide, via two routes that predate that fix and were not updated alongside it.

## Affected products

| Field | Value |
|---|---|
| Ecosystem | **Go** |
| Package name | `github.com/siyuan-note/siyuan/kernel` |
| Affected versions | Present as of commit `251596f` (2026-08-12, the version this review confirmed), i.e. postdates and was not covered by the `GHSA-c8r8-95hg-mp34` fix (commit `3542530`, 2026-08-08) |
| Patched versions | *(none yet, leave blank until a fix is released)* |

## Severity

| Field | Value |
|---|---|
| Vector string | `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:M/I:N/A:N` |
| Score | **~5.9 (Medium)**, `PR:H` since admin authentication is required at the HTTP layer, confidentiality impact scoped to whatever sensitive historical content happens to exist in the tracked snapshots for a given deployment (a real but deployment-dependent condition, honestly reflected as Medium rather than assumed to always be present), no integrity/availability impact since both are read-only. |

## Weaknesses (CWE)

- **CWE-862**: Missing Authorization (primary)
- **CWE-200**: Exposure of Sensitive Information to an Unauthorized Actor

## Notes for filing
- Direct, narrow follow-up to `GHSA-c8r8-95hg-mp34`; recommend
  referencing that advisory directly when filing, since this is
  precisely the "sibling caller missed" pattern that fix's own
  centralization (moving the check into a shared `util` function) was
  presumably intended to prevent, just for two callers that existed
  before the shared function did and weren't migrated to it.
- Suggested fix: add `if util.IsForbiddenAbsPath(p) { ... reject ... }`
  to both handlers, matching the pattern already applied in
  `kernel/api/file.go` and `kernel/mcp/tools/file.go`.