# CVE-2026-51584: usememos Memos SSO account takeover via identifier mismatch

Source: https://junglewise.ai/threats/cve-2026-51584-usememos-memos-sso-account-takeover-via-identifier-mismatch  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-11. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-51584 · Severity: critical · CVSS 9.8 · Published 2026-08-11

Memos is an open-source note-taking application that supports single sign-on (SSO) for user authentication. A critical flaw allows attackers to take over any user account—including admin accounts—by manipulating their identity provider username or email to match a victim's Memos username, without requiring access to the victim's account or credentials.

Technologies: [Usememos Memos](https://junglewise.ai/threats/technologies/memos). Vendors: [Usememos](https://junglewise.ai/threats/vendors/usememos).

## Quick answers

**Is CVE-2026-51584 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51584 being exploited in the wild.

**How severe is CVE-2026-51584?** Critical severity, with a CVSS score of 9.8, published 11 August 2026.

**Which products and versions are affected?** Usememos Memos ≤ v0.27.1.

**Is there a fix for CVE-2026-51584?** A patch was published on 2026-04-23: Fixed in v0.28.0 via commit d688914b Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-51584 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-51584?** Check whether you run Usememos Memos at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authentication bypass (CWE-287 / CWE-284) in the SSO sign-in handler (server/router/api/v1/auth_service.go). When SSO is enabled, the application resolves local user accounts using only the identity provider's identifier (e.g., username, email, preferred_username) as a lookup key, without binding to the IdP's stable subject claim (sub). An unauthenticated remote attacker can exploit this by setting their identifier on any configured public IdP to match a victim's Memos username, completing the OAuth2 authorization flow, and receiving a valid session token for the victim's account. The attack requires knowledge of a target username and a configured public IdP, but no prior access. The vulnerability was patched in v0.28.0 by introducing a user_identity table that binds external identities to local users via stable subject claims.

## Affected products

- usememos Memos ≤ v0.27.1

## Timeline

- 2026-08-11: disclosed: Advisory published on NVD
- 2026-04-23: patched: Fixed in v0.28.0 via commit d688914b

## References

- [https://gist.github.com/seiyaibuki0523/33a4c06eb7d10914e5e5152ecd5100ec](https://gist.github.com/seiyaibuki0523/33a4c06eb7d10914e5e5152ecd5100ec)
- [https://github.com/usememos/memos](https://github.com/usememos/memos)

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