Skip to main content

Boteraser | Website and Server Security Solutions

🛡️ CVE-2026-45281 — nextcloud

🟠 CVSS 8.1 — High ✅ No Known Exploit NVD
8.1
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update

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, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the calendar, they would be able to view and modify it. 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, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Affected software

CVE-2026-45281 is recorded against 2 packages.

  • nextcloud
  • nextcloud-server (from 33.0.0 up to 33.0.3)

Timeline and source

Published on 12 July 2026 and last revised on 13 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
hackerone.com (Web)
nvd.nist.gov (Web)

Other advisories for this package

nextcloud has other advisories on record. If you are patching this one, these are worth checking on the same host:

Details

Severity HIGH
CVSS Score 8.1
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2026-07-12
Updated 2026-08-20
Modified 2026-07-13

Affected Packages

Software From version Fixed in
nextcloud — —
nextcloud-server 33.0.0 33.0.3

Similar Threats

Site Security Check

Is nextcloud part of your stack?

CVE-2026-45281 is rated CVSS 8.1 High. BotEraser scans your installation against known CVE records and tells you whether this vulnerability applies to the versions you actually run.

Scan My Site Free →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

Browse related advisories

All advisoriesCVECVE 2026
✓