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🛡️ CVE-2025-66546 — calendar

🟢 CVSS 3.3 — Low ✅ No Known Exploit CWE-639 NVD
3.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.19, 5.5.6, and 6.0.1, the calendar app allowed blindly booking appointments with a squential ID without known the appointment token. This vulnerability is fixed in 4.7.19, 5.5.6, and 6.0.1.

How this vulnerability can be exploited

This issue can be reached with local access to the system, 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 low, integrity none, availability none.

CVSS metrics in full

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

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • 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: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2025-66546 is classified as CWE-639: Authorization Bypass Through User-Controlled Key. An object is selected by an identifier from the request without checking the caller owns it.

Affected software

CVE-2025-66546 is recorded against 1 package.

  • calendar

Timeline and source

Published on 5 December 2025 and last revised on 17 June 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
github.com
github.com
hackerone.com

Other advisories for this package

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

Same weakness in other software

These advisories are the same class of weakness (CWE-639: Authorization Bypass Through User-Controlled Key) in other software:

Details

Severity LOW
CVSS Score 3.3
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CWE CWE-639
Public Exploit ✅ No
Source NVD
Published 2025-12-05
Updated 2026-08-20
Modified 2026-06-17

Affected Packages

Software From version Fixed in
calendar — —

Similar Threats

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ⓘ 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.

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