CVE-2026-45690: Nextcloud: Two-Factor Authentication Bypass via Pending Session Token Replay

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-01 · updated 2026-07-22
Weakness: CWE-287

Description

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, an authentication bypass vulnerability allowed attackers with knowledge of a user's password to circumvent two-factor authentication (2FA) protections. When a user initiated login with valid credentials on a 2FA-enabled account, the system created a temporary session token before enforcing the second factor challenge. This token could be extracted and replayed via HTTP Basic Authentication to gain unauthorized access to authenticated endpoints. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9 or 29.0.16.16

Affected products

Nextcloud Server: from 32.0.0 before 32.0.9; from 33.0.0 before 33.0.3; from 29.0.0 before 29.0.16.16; from 30.0.0 before 30.0.17.9; from 31.0.0 before 31.0.14.5 — fixed in 29.0.16.16, 30.0.17.9, 31.0.14.5, 32.0.9, 33.0.3

How to fix

Upgrade to a fixed version: Nextcloud Server 29.0.16.16, 30.0.17.9, 31.0.14.5, 32.0.9. Check the vendor advisory for mitigations.

References

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