CVE-2026-76216Network attack vector

Cross-account actions via LinkShare ID collision

Published Aug 19, 2026 · Updated Aug 20, 2026

Authorization bypass in Vikunja through 2.4.0 allows remote authenticated users with a LinkSharing JWT to alter team or bot state or read team data. The vulnerable permission checks in TeamMember.CanDelete, BotUser.isOwner, and Team.CanRead compare web.Auth.GetID() directly to user-owned identifiers, so a LinkSharing principal whose positive share ID collides with a users.id value is treated as that unrelated user without a LinkSharing type guard. Exploitation requires link sharing to be enabled, which the advisory states is the default, and a colliding share ID; the published impact is limited to removing victims from teams, enumerating or deleting victim bot users, and reading team rosters and metadata.

CVSS severity7.7
High
EPSS probability0.26%
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 Vikunja through 2.4.0 allows remote authenticated users with a LinkSharing JWT to alter team or bot state or read team data. The vulnerable permission checks in TeamMember.CanDelete, BotUser.isOwner, and Team.CanRead compare web.Auth.GetID() directly to user-owned identifiers, so a LinkSharing principal whose positive share ID collides with a users.id value is treated as that unrelated user without a LinkSharing type guard. Exploitation requires link sharing to be enabled, which the advisory states is the default, and a colliding share ID; the published impact is limited to removing victims from teams, enumerating or deleting victim bot users, and reading team rosters and metadata.

The record

CVE
CVE-2026-76216
Published
Aug 19, 2026
Updated
Aug 20, 2026
Vendor
Vikunja
Product
Vikunja
Classifications
CWE-639
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2026Record 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=0 <=2.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Vikunja · Vikunjaversion=0 <=2.4.0

Published CVSS scores

7.5VulnCheckCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.7VulnCheckCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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

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