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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2026-63095

MEDIUM · 6.5 CVSS v3.1 Developing Published 2026-07-17
No fix yet
No fix has been published. The vendor has not shipped a fixed release or patch. You remain exposed.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-07-31.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Recommended fix Moderate confidence

Dendrite 0.13.9 or later stable release

  1. 1. Identify the current Dendrite version running in your environment using system logs or package management tools.
  2. 2. Obtain the latest stable Dendrite release from the official Dendrite repository (github.com/matrix-org/dendrite).
  3. 3. Review the Dendrite release notes or changelog for version 0.13.9 or later to confirm the authorization fix for the Forget3PID handler vulnerability.
  4. 4. Plan a maintenance window for the upgrade, ensuring appropriate backups of configuration and database files exist.
  5. 5. Stop the Dendrite service before performing the upgrade.
  6. 6. Upgrade Dendrite to version 0.13.9 or the latest stable release that includes the security fix.
  7. 7. Verify the configuration files remain intact after upgrade.
  8. 8. Start the Dendrite service and monitor logs for any errors.
Caveat Review release notes for potential breaking changes between 0.13.8 and the target upgrade version; test in staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

No vendor fix exists The vendor has not published a patch for this.

There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-63095 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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