CVE-2025-66556Network attack vector

Cross-user poll deletion via missing moderator check

Published Dec 5, 2025 · Updated Dec 5, 2025

Authorization bypass in Nextcloud Talk before 20.1.8 and in the 21.x branch before 21.1.2 allows remote authenticated users to delete poll drafts. PollController::closePoll deleted a draft selected by numeric poll ID without checking whether the requesting participant had moderator permissions. Conversation membership with chat permissions and another participant's draft ID were sufficient to remove that draft; published evidence reports no broader impact.

CVSS severity3.5
Low
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Authorization bypass in Nextcloud Talk before 20.1.8 and in the 21.x branch before 21.1.2 allows remote authenticated users to delete poll drafts. PollController::closePoll deleted a draft selected by numeric poll ID without checking whether the requesting participant had moderator permissions. Conversation membership with chat permissions and another participant's draft ID were sufficient to remove that draft; published evidence reports no broader impact.

The record

CVE
CVE-2025-66556
Published
Dec 5, 2025
Updated
Dec 5, 2025
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-639, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 5, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 20.1.8
  2. Affected versionversion=>= 21.0.0-beta.1, < 21.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=< 20.1.8; version=>= 21.0.0-beta.1, < 21.1.2

Published CVSS scores

3.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo