# GHSA-7v7m-pcw5-h3cg: Pusher Service Channel Authentication Bypass

> A malicious user with access to one private channel can forge tokens to access other private channels or authenticate API requests due to insufficient socket_id validation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 May 2024

## What is GHSA-7v7m-pcw5-h3cg?

GHSA-7v7m-pcw5-h3cg is an authentication bypass vulnerability in pusher/pusher-php-server, published on 20 May 2024. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The service offered by Pusher provides "private" channels with an authentication mechanism that restricts subscription access. The decision on allowing subscriptions to private channels is delegated to customers, who implement an authentication endpoint. End-users request a token from this endpoint to join a specific channel. The token is an HMAC signature of the end-user's connection ID (socket_id) and the desired channel.

The issue arises from a lack of validation in the libraries provided to customers. This vulnerability allows a malicious end-user to submit a malformed socket_id field, leading the customer to unknowingly sign a string. This signed string grants access to a different private channel than the one the end-user is ostensibly requesting. Consequently, a malicious end-user, with permission to subscribe to one private channel, can forge permission for any private channel owned by the same customer.

Additionally, the HTTP API is secured by requiring a signature with each request, generated by the customer's secret key. In specific cases, a malicious end-user may deceive a customer into signing a value for socket_id, effectively authenticating an API request to Pusher.

## Which versions are affected by GHSA-7v7m-pcw5-h3cg?

2 open source packages ship an affected version, including pusher/pusher-php-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pusher/pusher-php-server` | Packagist | All versions | 2.2.1 |
| `pusher/pusher-php-server` | Packagist | All versions | 2.2.1 |

## How do I fix GHSA-7v7m-pcw5-h3cg?

Upgrade pusher/pusher-php-server to 2.2.1 or later.

## Is GHSA-7v7m-pcw5-h3cg being exploited?

There is no known exploitation of GHSA-7v7m-pcw5-h3cg in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-7v7m-pcw5-h3cg and fix it if it is affected.

What it is: GHSA-7v7m-pcw5-h3cg is an authentication bypass vulnerability in pusher/pusher-php-server, published on 20 May 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-7v7m-pcw5-h3cg in the wild and no public exploit code.

Affected packages and fixed versions:
- pusher/pusher-php-server (Packagist): affected all versions; fixed in 2.2.1
- pusher/pusher-php-server (Packagist): affected all versions; fixed in 2.2.1

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/GHSA-7v7m-pcw5-h3cg/ (Markdown: https://insights.sbomify.com/GHSA-7v7m-pcw5-h3cg/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-7v7m-pcw5-h3cg

---
From sbomify Insights: https://insights.sbomify.com/GHSA-7v7m-pcw5-h3cg/
Summaries are generated and may contain mistakes; the official description above is the record.