---
id: GHSA-w67g-5rqw-f597
title: Gorilla WebSocket Uses Cryptographically Weak PRNG for WebSocket Mask Key
summary: Gorilla WebSocket Uses Cryptographically Weak PRNG for WebSocket Mask Key
severity: medium
cwe:
  - CWE-338
vendor: gorilla
product: github.com/gorilla/websocket
ecosystem: go
affected:
  - github.com/gorilla/websocket < 1.5.3
patched:
  - github.com/gorilla/websocket 1.5.3
published: '2026-08-24'
updated: '2026-08-24'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-w67g-5rqw-f597'
references:
  - url: >-
      https://github.com/canolgun-commits/websocket/security/advisories/GHSA-w67g-5rqw-f597
  - url: >-
      https://github.com/gorilla/websocket/commit/d67f41855da42d7bccd9ef050c49f7e54e783b95
  - url: 'https://github.com/gorilla/websocket/releases/tag/v1.5.3'
  - url: 'https://github.com/advisories/GHSA-w67g-5rqw-f597'
tags:
  - ghsa
  - go
ingestedAt: '2026-08-24T21:11:25.037Z'
---

## Overview

gorilla/websocket used `math/rand` (cryptographically weak pseudo-random number generator) to generate WebSocket frame mask keys prior to commit d67f4185. WebSocket masking keys MUST be unpredictable to prevent frame content injection attacks. math/rand produces deterministic output when seeded with a known value, enabling an attacker to predict or recover mask keys and inject content into WebSocket connections.

**Type:** Use of Cryptographically Weak Pseudo-Random Number Generator
**Fix:** Replaced math/rand with crypto/rand (commit d67f4185, released in v1.5.3)
**Credit:** bounty-hunter v6.0 silent-fix detection

## Affected packages

- `github.com/gorilla/websocket < 1.5.3`

## Remediation

Upgrade to a patched release:

- `github.com/gorilla/websocket 1.5.3`