# CVE-2026-58593: NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User

> Remote attackers can forge posts and messages attributed to arbitrary local users, including admins, by exploiting unvalidated ActivityPub author fields.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 7 Jul 2026
- **Also known as:** GHSA-8m27-grg5-27vj

## What is CVE-2026-58593?

CVE-2026-58593 is a high-severity missing authorization vulnerability in NodeBB, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NodeBB does not bind the claimed author of an inbound ActivityPub object to the authenticated remote actor. The inbound middleware verifies the HTTP-signature actor and checks the origin of object.id, but never validates that attributedTo corresponds to the sender. In the object mock, attributedTo is used directly as a uid, and actors.assert silently ignores numeric identifiers (filtering them out without re-deriving the uid), so a federated remote actor can set attributedTo to a bare numeric value such as 1 and have the resulting post or private message created with that local uid as author, including the administrator account. This lets a remote attacker forge posts and direct messages attributed to arbitrary local users. Requires the ActivityPub/federation feature to be enabled.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity), CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-58593?

It affects 1 product.


Products: Nodebb Nodebb.

## How do I fix CVE-2026-58593?

No fix has been published for CVE-2026-58593 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-58593 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58593 exists.

## Other vulnerabilities in NodeBB

- [CVE-2023-26045](https://insights.sbomify.com/CVE-2023-26045/): NodeBB vulnerable to path traversal and code execution via prototype vulnerability (critical 10.0)
- [CVE-2020-15149](https://insights.sbomify.com/CVE-2020-15149/): Account takeover in NodeBB (critical 9.9)
- [CVE-2023-43187](https://insights.sbomify.com/CVE-2023-43187/): Code injection in n/a (critical 9.8)
- [CVE-2021-43786](https://insights.sbomify.com/CVE-2021-43786/): API token verification can be bypassed (critical 9.8)
- [CVE-2022-46164](https://insights.sbomify.com/CVE-2022-46164/): Account takeover via prototype vulnerability (critical 9.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58593 and fix it if it is affected.

What it is: CVE-2026-58593 is a high-severity missing authorization vulnerability in NodeBB, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58593 exists.

Affected product: NodeBB. 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-2026-58593/ (Markdown: https://insights.sbomify.com/CVE-2026-58593/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58593
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58593
- OSV: https://osv.dev/vulnerability/CVE-2026-58593

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58593/
Summaries are generated and may contain mistakes; the official description above is the record.