CVE-2026-45691 | 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

Published: 2026-06-01 Last update: 2026-06-04 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-45691 is rated Low Risk (29.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.06%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-45691

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-02 — 0.06% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-45691

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 1.6 4.2 [email protected]

Weakness enumeration for CVE-2026-45691

Affected software / configurations for CVE-2026-45691

Vendor Product Version Raw CPE
nextcloud nextcloud_server >= 32.0.0, < 32.0.9 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:*
nextcloud nextcloud_server >= 33.0.0, < 33.0.3 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:*
nextcloud nextcloud_server >= 29.0.0, < 29.0.16.16 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*
nextcloud nextcloud_server >= 30.0.0, < 30.0.17.9 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*
nextcloud nextcloud_server >= 31.0.0, < 31.0.14.5 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*
nextcloud nextcloud_server >= 32.0.0, < 32.0.9 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*
nextcloud nextcloud_server >= 33.0.0, < 33.0.3 cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*

References for CVE-2026-45691

cvelogic Threat Intelligence