# CVE-2026-100355: Campfire vulnerable to SSRF via incomplete private-network denylist in the link-unfurl guard

> CVE-2026-100355: Campfire vulnerable to SSRF via incomplete private-network denylist in the link-unfurl guard. CVSS 3.1 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-100355
Last updated: 2026-10-30T19:39:14Z

- Published: 2026-10-30 14:10 UTC · Updated: 2026-10-30 19:39 UTC · Assigner: GitHub\_M
- CVSS: 3.1 (CVSS 3.1) · Severity: Low · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
- EPSS: 0.28%, 21th percentile (scored 2026-11-04)
- CISA KEV: no
- CWE: CWE-918

## 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.

## Affected vendors and products

- basecamp: once-campfire

## Tracked companies

- [Basecamp](https://rewindex.com/company/basecamp.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-100355)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-100355)
- [https://github.com/basecamp/once-campfire/commit/69e8cd788593cf421c32626a5273c0b449ceee9b](https://github.com/basecamp/once-campfire/commit/69e8cd788593cf421c32626a5273c0b449ceee9b)
- [https://github.com/basecamp/once-campfire/pull/225](https://github.com/basecamp/once-campfire/pull/225)
- [https://github.com/basecamp/once-campfire/releases/tag/v1.4.5](https://github.com/basecamp/once-campfire/releases/tag/v1.4.5)
- [https://github.com/basecamp/once-campfire/security/advisories/GHSA-gjm7-g266-w3wj](https://github.com/basecamp/once-campfire/security/advisories/GHSA-gjm7-g266-w3wj)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-100355 · Markdown: https://rewindex.com/cve/CVE-2026-100355.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-100355 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-04T16:19:36.529Z