CVE-2026-45691 Nextcloud: Bypass of second factor authentication on DAV endpoints
Attackers can bypass two-factor authentication on DAV endpoints by reusing pre-2FA session cookies as Bearer tokens, gaining unauthorized read and write access.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45691?
CVE-2026-45691 is a medium-severity authentication bypass vulnerability in Nextcloud Nextcloud Server, published on 1 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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, a pre-2FA session cookie (created after successful password authentication but before TOTP completion) could be reused as a Bearer token to authenticate against DAV endpoints, granting read/write access and bypassing mandatory two-factor authentication. 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
Weakness: CWE-287
Which versions are affected by CVE-2026-45691?
1 open source package ship an affected version, including nextcloud. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nextcloud Bitnami | From 32.0.0 | 32.0.9, 33.0.3 |
Products include Nextcloud Nextcloud Server.
How do I fix CVE-2026-45691?
Upgrade nextcloud to a fixed version for your release line: 32.0.9 or 33.0.3.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-45691 being exploited?
There is no known exploitation of CVE-2026-45691 in the wild and no public exploit code.
Other vulnerabilities in Nextcloud Nextcloud Server
- CVE-2021-32802 Preview generation used third-party library not suited for user-generated content in Nextcloud server
- CVE-2023-26482 Scope of workflow operations is not validated in nextcloud server
- CVE-2018-3775 Auth bypass in Nextcloud Server
- CVE-2023-35172 Nextcloud Server password reset endpoint is not brute force protected
- CVE-2023-32320 Nextcloud Server's brute force protection allows someone to send more requests than intended
Sources
Also known as BIT-nextcloud-2026-45691, GHSA-mp6x-g55j-w9jw.