---
id: CVE-2026-100355
title: >-
  Campfire vulnerable to SSRF via incomplete private-network denylist in the
  link-unfurl guard
summary: >-
  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#p…
severity: low
cvss: 3.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N'
cvssSource: cna
cwe:
  - CWE-918
vendor: basecamp
product: once-campfire
affected:
  - once-campfire < 1.4.5
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:29:32.090726Z'
published: '2026-10-30'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:29:44.987Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-100355'
references:
  - url: >-
      https://github.com/basecamp/once-campfire/security/advisories/GHSA-gjm7-g266-w3wj
    label: >-
      https://github.com/basecamp/once-campfire/security/advisories/GHSA-gjm7-g266-w3wj
  - url: 'https://github.com/basecamp/once-campfire/pull/225'
    label: 'https://github.com/basecamp/once-campfire/pull/225'
  - url: >-
      https://github.com/basecamp/once-campfire/commit/69e8cd788593cf421c32626a5273c0b449ceee9b
    label: >-
      https://github.com/basecamp/once-campfire/commit/69e8cd788593cf421c32626a5273c0b449ceee9b
  - url: 'https://github.com/basecamp/once-campfire/releases/tag/v1.4.5'
    label: 'https://github.com/basecamp/once-campfire/releases/tag/v1.4.5'
tags:
  - cve.org
epss: 0.00279
epssPercentile: 0.20498
ingestedAt: '2026-11-05T16:07:30.283Z'
---

## Overview

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.

## Affected

- `once-campfire < 1.4.5`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.