Vulnerability · Published Jun 1, 2026 · Assigned by GitHub_M
CVE-2026-45156Nextcloud: Authentication Bypass in ID4me handling via Missing JWT Signature Verification in User OIDC
High 8.1
In plain English
A high-severity improper authentication in security-advisories from nextcloud. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official description
Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| nextcloud | security-advisories | >= 0.3.0, < 3.1.0>= 5.0.0, < 5.1.0>= 6.0.0, < 6.4.0 |
Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
References
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qqgv-fqwp-mjpp x_refsource_CONFIRM
- https://github.com/nextcloud/user_oidc/pull/1285 x_refsource_MISC
- https://hackerone.com/reports/3489490 x_refsource_MISC