---
id: "CVE-2026-100355"
kind: "vulnerability"
aliases: ["CVE-2026-100355"]
title: "Campfire chat: link previews reach internal addresses through special-use ranges"
severity: "low"
cvss: 3.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["campfire", "package", "ruby", "self-hosted"]
not_affected_if: ["auth-required", "version-1.4.5-or-later"]
published_at: "2026-10-30T14:16:35+00:00"
first_seen_at: "2026-10-30T14:30:53+00:00"
updated_at: "2026-10-30T14:33:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-100355", "first_seen_at": "2026-10-30T14:30:53+00:00"}]
---

# Campfire chat: link previews reach internal addresses through special-use ranges

Campfire fetches links posted in chat to build preview cards, and its guard against internal addresses misses CGNAT, NAT64 and 6to4 ranges. An authenticated user can make the server request internal resources and see OpenGraph metadata returned from them.

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

## How to check

- Check the installed Campfire version and whether it is `1.4.4` or earlier
- Confirm whether link unfurling is enabled in your deployment (unknown from the sources)

## Fix

- Campfire: move to `1.4.5` (the sources say an initial fix was released in this version; later fixes are unknown)

## Timeline

- 2026-10-30T14:30:53+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-100355

## From the sources

Campfire is a web-based chat application. In version 1.4.4 and earlier, when a Campfire message contains a link, the server fetches it to build an OpenGraph unfurl preview. `RestrictedHTTP::PrivateNetworkGuard` relied on Ruby's `IPAddr#private? `` IPAddr#loopback?`, and `IPAddr#link_local?` predicates plus IPv4-mapped and IPv4-compatible checks, which do not cover several special-use ranges. An authenticated user can post a link to a hostname resolving to CGNAT `100.64.0.0/10`, NAT64 `64:ff9b::/96` or `64:ff9b:1::/48`, or 6to4 `2002::/16` to bypass the guard and cause server-side requests to internal network resources. The NAT64 and 6to4 ranges can embed an internal IPv4 target. Confidentiality impact is limited to returned OpenGraph metadata, and most internal endpoints return none. There is no integrity or availability impact. An initial fix was released in version 1.4.5.

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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_