CVE-2026-55066Public exploitNetwork attack vectorHinoki check available

Cross-tenant task read and write via unchecked identifier

Published Aug 28, 2026 · Updated Aug 28, 2026

Authorization bypass in Vikunja before 2.4.0 allows remote authenticated users to read and modify cross-tenant tasks via a task ID. TaskBucket.CanUpdate validates only the URL-selected project, view, and bucket, while updateTaskBucket loads the body-supplied task_id without checking task permissions. Any account can enumerate sequential task IDs, receive full victim task contents, and alter completion metadata by selecting a done bucket.

CVSS severity7.1
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authorization bypass in Vikunja before 2.4.0 allows remote authenticated users to read and modify cross-tenant tasks via a task ID. TaskBucket.CanUpdate validates only the URL-selected project, view, and bucket, while updateTaskBucket loads the body-supplied task_id without checking task permissions. Any account can enumerate sequential task IDs, receive full victim task contents, and alter completion metadata by selecting a done bucket.

The record

CVE
CVE-2026-55066
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Vikunja
Product
Vikunja
Classifications
CWE-639, T1213, T1565
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=< 2.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Vikunja · Vikunjaversion=< 2.4.0

Published CVSS scores

7.1GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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.

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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 exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1213Data from Information Repositories
T1565Data Manipulation

Public exploit references

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

Technologies

Your stack

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Your stack

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