# CVE-2026-73310: XenForo < 2.3.13 OAuth2 Authorization Code Token Theft via redirect_uri Bypass

> Attackers can steal OAuth2 tokens by bypassing redirect URI validation, leading to account takeover and data access in XenForo.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/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:** 8 Sep 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-3hj9-69jw-9xx6

## What is CVE-2026-73310?

CVE-2026-73310 is a high-severity authentication bypass vulnerability in XenForo, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

XenForo before 2.3.13 contains an authorization flaw in the OAuth2 token endpoint that allows attackers controlling any allowlisted redirect URI to bypass redirect URI binding by submitting a different allowlisted URI than the one recorded at authorization time. Attackers can exchange an intercepted authorization code using a mismatched redirect URI to steal OAuth2 tokens from intercepted authorization flows.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-73310?

It affects 1 product.


Products: Xenforo Xenforo.

## How do I fix CVE-2026-73310?

No fix has been published for CVE-2026-73310 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-73310 being exploited?

There is no known exploitation of CVE-2026-73310 in the wild and no public exploit code.

Public exploit code:

- Sanitized XenForo write-up and proof of concept for CVE-2026-73310. (github_poc): https://github.com/BomboBombone/CVE-2026-73310

## Other vulnerabilities in XenForo

- [CVE-2025-71279](https://insights.sbomify.com/CVE-2025-71279/): XenForo Passkey Security Bypass (critical 9.3)
- [CVE-2026-73309](https://insights.sbomify.com/CVE-2026-73309/): XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint (critical 9.1)
- [CVE-2026-73311](https://insights.sbomify.com/CVE-2026-73311/): XenForo < 2.3.13 OAuth2 Authorization Code Reuse (critical 9.1)
- [CVE-2026-73312](https://insights.sbomify.com/CVE-2026-73312/): XenForo < 2.3.13 Refresh Token Replay via Expired Access Token (critical 9.1)
- [CVE-2024-38457](https://insights.sbomify.com/CVE-2024-38457/): Xenforo before 2.2.16 allows CSRF. (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73310 and fix it if it is affected.

What it is: CVE-2026-73310 is a high-severity authentication bypass vulnerability in XenForo, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-73310 in the wild and no public exploit code.

Affected product: XenForo. 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-2026-73310/ (Markdown: https://insights.sbomify.com/CVE-2026-73310/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73310
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73310
- OSV: https://osv.dev/vulnerability/CVE-2026-73310

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73310/
Summaries are generated and may contain mistakes; the official description above is the record.