# CVE-2026-82843: WP OAuth Server < 6.4.0 - Subscriber+ Cross-User Account Takeover via OIDC ID Token Substitution

> Subscribers can impersonate administrators by exploiting OIDC token substitution flaws in the WP OAuth Server plugin, leading to full account takeover.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 23 Sep 2026
- **Updated:** 23 Sep 2026
- **Also known as:** GHSA-rwfr-37x7-2rr8

## What is CVE-2026-82843?

CVE-2026-82843 is a critical authentication bypass vulnerability in Unknown WP OAuth Server ( Login with WordPress ), published on 23 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

The WP OAuth Server ( Login with WordPress ) WordPress plugin before 6.4.0 does not bind the OpenID Connect identity assertion it issues to the authorization grant being exchanged, returning instead the assertion belonging to whichever user authenticated most recently, which allows users with the Subscriber role and above to obtain a validly signed identity assertion for another user, including an administrator, and authenticate as them at any application that uses the site for single sign-on.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-82843?


## How do I fix CVE-2026-82843?

No fix has been published for CVE-2026-82843 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-82843 being exploited?

There is no known exploitation of CVE-2026-82843 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82843 and fix it if it is affected.

What it is: CVE-2026-82843 is a critical authentication bypass vulnerability in Unknown WP OAuth Server ( Login with WordPress ), published on 23 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-82843 in the wild and no public exploit code.

Affected product: Unknown WP OAuth Server ( Login with WordPress ). 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-2026-82843/ (Markdown: https://insights.sbomify.com/CVE-2026-82843/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82843
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82843
- OSV: https://osv.dev/vulnerability/CVE-2026-82843

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82843/
Summaries are generated and may contain mistakes; the official description above is the record.