---
id: "CVE-2026-93857"
kind: "vulnerability"
aliases: ["CVE-2026-93857"]
title: "Fireware OS: SIP proxy buffer overflow lets unauthenticated remote attackers run code"
severity: "critical"
cvss: 9.2
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["firewall", "fireware-os", "infrastructure", "network-appliance", "sip", "watchguard"]
not_affected_if: ["no-sip-proxy-policy", "patched-firmware"]
published_at: "2026-10-27T16:17:32+00:00"
first_seen_at: "2026-10-27T16:33:07+00:00"
updated_at: "2026-10-27T16:33:59+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93857", "first_seen_at": "2026-10-27T16:33:07+00:00"}]
---

# Fireware OS: SIP proxy buffer overflow lets unauthenticated remote attackers run code

A stack-based buffer overflow in the SIP proxy of Fireware OS, the firmware for WatchGuard firewalls, can be triggered by a specially crafted request sent through a policy that uses the SIP proxy. A remote, unauthenticated attacker can execute arbitrary code on the appliance.

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

## How to check

- Check the installed Fireware OS version on the appliance (unknown for exact affected range; sources do not list it)
- Check whether any firewall policy uses the SIP proxy (unknown; sources do not say how to see this in the UI)

## Fix

- Move Fireware OS to a patched release (unknown; the sources do not name the fixed version)
- Disable or remove firewall policies that use the SIP proxy until patched (inferred from the description; confirm with vendor advisory)

## Timeline

- 2026-10-27T16:33:07+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93857

## From the sources

A stack-based buffer overflow vulnerability in Fireware OS's SIP proxy allows a remote, unauthenticated attacker to execute arbitrary code by sending a specially crafted request through a policy that uses the SIP proxy.

---

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