# CVE-2026-104978: Plane: Invitation Hijack in Project Join Flow via Missing Authorization and Email-Only Acceptance

> Attackers can hijack project invitations by registering with an invited email, gaining unauthorized access to workspaces and projects.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Oct 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-g36h-p63v-g9c7

## What is CVE-2026-104978?

CVE-2026-104978 is a high-severity missing authorization vulnerability in makeplane plane, published on 5 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Plane is an open-source project management tool. Prior to 1.4.0, Plane's project invitation list endpoint is accessible to any authenticated user who knows the workspace slug and project ID, while the public project invitation join endpoint accepts an invitation based only on a submitted email address. When a pending invitation targets an email address that has not registered with Plane, an attacker can enumerate the invitation, register an account using the invited email without mailbox verification, and accept the invitation. The attacker-controlled account is then added to the target workspace and project. This issue is fixed in 1.4.0.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-104978?


## How do I fix CVE-2026-104978?

No fix has been published for CVE-2026-104978 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104978 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-104978 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104978 and fix it if it is affected.

What it is: CVE-2026-104978 is a high-severity missing authorization vulnerability in makeplane plane, published on 5 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-104978 exists.

Affected product: makeplane plane. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-104978/ (Markdown: https://insights.sbomify.com/CVE-2026-104978/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104978
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104978
- OSV: https://osv.dev/vulnerability/CVE-2026-104978

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104978/
Summaries are generated and may contain mistakes; the official description above is the record.