CVE-2026-100355
Received Received - Intake

Server-Side Request Forgery in Campfire via Special-Use IP Ranges

Publication date: 2026-10-30

Last updated on: 2026-10-30

Assigner: GitHub, Inc.

Description
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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Meta Information

Published
2026-10-30
Last Modified
2026-10-30
Generated
2026-10-30
AI Q&A
2026-10-30
EPSS Evaluated
N/A
NVD
CVE-2026-100355
EUVD
EUVD-2026-114058

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
basecamp once-campfire < 1.4.5

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

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Executive Summary

This vulnerability affects Campfire, a web-based chat app. In versions 1.4.4 and earlier, the server fetches links in messages to create OpenGraph previews. A flaw in the network guard allowed bypassing restrictions for special IP ranges like CGNAT, NAT64, or 6to4, enabling server-side requests to internal resources.

Detection Guidance

This vulnerability involves server-side requests to internal resources via special-use IP ranges. Detect it by monitoring outbound HTTP requests from your Campfire server to addresses in 100.64.0.0/10, 64:ff9b::/96, 64:ff9b:1::/48, or 2002::/16. Check server logs for OpenGraph unfurl requests to these ranges.

Impact Analysis

An authenticated user could exploit this to make the server access internal network resources. Confidentiality may be impacted if OpenGraph metadata from internal endpoints is exposed. No integrity or availability risks are noted.

Mitigation Strategies

Upgrade Campfire to version 1.4.5 or later to address the issue. If immediate upgrade is not possible, restrict outbound requests from the server to internal networks and block access to the special-use IP ranges mentioned in the vulnerability description.

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