VulnerabilityPublished 15 Sep 2026

CVE-2026-91983: vikunja · Incorrect Authorization

Affects vikunjaSource CVE Database V5

Compare

Not known to be exploited · CVSS 5.3 Medium : upgrade to 2.6.0 when convenient.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.6.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade vikunja and github.com/go-vikunja/vikunja to 2.6.0.

Affected software

Product	Affected	Fixed in
go-vikunjavikunja	Affected >=1.0.0 <2.6.0	Fixed in 2.6.0
Gogithub.com/go-vikunja/vikunja`pkg:golang/github.com/go-vikunja/vikunja`Other threats	Affected >=1.0.0 <2.6.0	Fixed in 2.6.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

The recommended fix is to enhance the authorization middleware to check the 'expand' query parameter and require the token to hold the corresponding read permissions for each expanded data group (e.g., comments, reactions, time entries). This fix can be implemented centrally in the existing authorization logic to cover all affected API versions without handler or model changes.

Description

## Summary API token permission checks only match the HTTP method and route path. The `expand` query parameter on task read endpoints embeds data from other permission groups (task comments, reactions, time entry counts) without checking whether the token holds those scopes. A token scoped only to `tasks` read permissions can therefore read task comments and reactions it was explicitly not granted. ## Details `models.CanDoAPIRoute` (`pkg/models/api_routes.go`, ~line 440) authorises API tokens purely by comparing `method` and `c.Path()` against the routes stored for each granted permission group. The query string is never consulted. The task read endpoints accept `expand`: - `GET /api/v1/tasks/:task`, `GET /api/v1/tasks` (`pkg/models/tasks.go` ReadOne/ReadAll, `pkg/models/task_collection.go`) - `GET /api/v2/tasks/:id`, `GET /api/v2/tasks`, `GET /api/v2/projects/:project/tasks` (`pkg/routes/api/v2/tasks.go`, `task_collection.go`) Accepted values include `comments`, `comment_count`, `reactions`, `time_entries_count`. `addMoreInfoToTasks` (`pkg/models/tasks.go`, ~line 683) loads and embeds that data. At that layer only a `web.Auth` (the plain owner user, resolved by `auth.GetAuthFromClaims`) is available, so the token's scopes cannot be enforced there either. Result: the `tasks_comments`, `reactions`, and `time_entries` permission groups are advisory for any data reachable through a task expansion. ## Impact A holder of an API token scoped to `tasks: [read_one]` or `tasks: [read_all]` (or `projects_views_tasks: [read_all]`) can read the full bodies of task comments, all reactions, and time entry counts on every task the token owner can access, despite `GET /api/v1|v2/tasks/:task/comments` and the reactions endpoints correctly returning 401 for the same token. The leak is limited to data the token owner can already see, and is read-only. The realistic victim is a user who grants a narrowly scoped token to a third-party integration expecting comments to stay private. ## Proof of Concept Against the test fixtures (`pkg/db/fixtures/api_tokens.yml`, token 1 has `{"tasks":["read_all","update"]}`, plaintext `tk_2eef46f40ebab3304919ab2e7e39993f75f29d2e`): ``` GET /api/v2/tasks/1/comments Authorization: Bearer tk_2eef46f40ebab3304919ab2e7e39993f75f29d2e -> 401 {"code":11,"message":"missing, malformed, expired or otherwise invalid token provided"} GET /api/v2/tasks?expand=comments&filter=id%3D1 Authorization: Bearer tk_2eef46f40ebab3304919ab2e7e39993f75f29d2e -> 200, response items[0].comments contains the full comment objects ``` Same behaviour with `expand=reactions`, and on the v1 endpoints `GET /api/v1/tasks?expand=comments` / `GET /api/v1/tasks/1?expand=comments`. Any user-created token with only `tasks` read permissions reproduces this. ## Recommended Fix Enforce expansions in the single existing choke point, `models.CanDoAPIRoute`: after the method/path match succeeds, read `c.QueryParams()["expand"]` and require the token to hold the owning group's read permission for each value, e.g. - `comments`, `comment_count` -> `tasks_comments.read_all` - `reactions` -> `reactions.read_all` - `time_entries_count` -> `time_entries.read_all` (`subtasks`, `buckets`, `is_unread` are task-level data and need nothing extra.) Doing this in the middleware covers both v1 and v2 without handler or model changes. Add a table-driven test alongside `pkg/webtests/api_token_method_matching_test.go` asserting a `tasks`-only token gets 401 with `expand=comments` and 200 once `tasks_comments.read_all` is added.

Impact

An API token with only task read permissions can read full task comments, reactions, and time entry counts through expanded task endpoints, bypassing intended permission restrictions. The data exposed is limited to what the token owner can already access, and the vulnerability does not allow modification or access beyond the token owner's scope. This may lead to unintended data disclosure to third-party integrations granted narrowly scoped tokens expecting comments and reactions to remain private.

Summary

The vulnerability in go-vikunja vikunja arises from the API token authorization logic in models.CanDoAPIRoute, which authorizes tokens solely based on HTTP method and route path, ignoring the 'expand' query parameter on task read endpoints. This allows a token scoped only for reading tasks to retrieve expanded data such as comments, reactions, and time entry counts without holding the required permissions for those data groups. The issue affects both v1 and v2 API endpoints and results in unauthorized read access to task-related data embedded via expansions. The recommended fix is to enforce permission checks on the 'expand' query parameter values in the authorization middleware, requiring tokens to hold the appropriate read permissions for each expanded data group.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Oct 2026, 22:48 UTC

Technical details

References

Community reviews

Related threats