Nextcloud Server 32/33: Session Cookie Reused as Bearer Token Bypass 2FA
CVE-2026-45691 Published on June 1, 2026
Nextcloud: Bypass of second factor authentication on DAV endpoints
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
Vulnerability Analysis
CVE-2026-45691 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a high impact on integrity, and no impact on availability.
Weakness Type
What is an authentification Vulnerability?
When an actor claims to have a given identity, the software does not prove or insufficiently proves that the claim is correct.
CVE-2026-45691 has been classified to as an authentification vulnerability or weakness.
Affected Versions
nextcloud security-advisories:- Version >= 32.0.0, < 32.0.9 is affected.
- Version >= 33.0.0, < 33.0.3 is affected.