CVE-2026-91981Network attack vectorHinoki check available

User enumeration via link-share token authorization bypass

Published Sep 15, 2026 · Updated Sep 15, 2026

Improper authorization in Vikunja before 2.6.0 allows remote attackers with read-only share links to enumerate project users. The v2 API project and global user-search handlers accept link-share principals without enforcing their intended user-only and project-scope authorization checks. Possession of a read-only share token is required; the project endpoint lists users, while global search confirms whether arbitrary usernames exist.

CVSS severityUnavailable
Unscored
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Improper authorization in Vikunja before 2.6.0 allows remote attackers with read-only share links to enumerate project users. The v2 API project and global user-search handlers accept link-share principals without enforcing their intended user-only and project-scope authorization checks. Possession of a read-only share token is required; the project endpoint lists users, while global search confirms whether arbitrary usernames exist.

The record

CVE
CVE-2026-91981
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Vikunja
Product
Vikunja
Classifications
T1087
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 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=0 <2.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Vikunja · Vikunjaversion=0 <2.6.0

Published CVSS scores

No CVSS assessment is available in this record.

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 exploitUnconfirmed

Weakness, pattern, technique

T1087Account Discovery

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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