---
id: "CVE-2020-5135"
kind: "vulnerability"
aliases: ["CVE-2020-5135"]
title: "SonicWall SonicOS: SonicWall SonicOS Buffer Overflow Vulnerability"
severity: "critical"
cvss: 9.8
epss: 0.26869
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "SonicWall SonicOS", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "firewall", "infrastructure", "ransomware", "self-hosted", "sonicos", "sonicwall"]
not_affected_if: ["default-config"]
published_at: "2020-10-12T11:15:12+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-5135", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-5135", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-5135", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# SonicWall SonicOS: SonicWall SonicOS Buffer Overflow Vulnerability

A buffer overflow in SonicWall SonicOS, the firewall operating system, lets a remote attacker crash the firewall with a malicious request and possibly run arbitrary code on it. CISA lists it as actively exploited and tags it with ransomware use.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:SonicWall SonicOS affected ? fixed ?

## How to check

Check the SonicOS version on the firewall management page (unknown which versions are affected in the sources)
Check CISA KEV entry for CVE-2020-5135 for vendor advisory link

## Fix

Apply the SonicWall SonicOS update that addresses CVE-2020-5135 per vendor instructions (exact fixed version unknown from sources)

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-5135
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-5135
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-5135

## From the sources

A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a malicious request to the firewall. This vulnerability affected SonicOS Gen 6 version 6.5.4.7, 6.5.1.12, 6.0.5.3, SonicOSv 6.5.4.v and Gen 7 version 7.0.0.0.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_