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Vulnerability · Published Oct 30, 2026 · Assigned by GitHub_M

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

Low 3.1

In plain English

A low-severity server-side request forgery in once-campfire from basecamp. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).

Severity (CVSS 3.1)3.1Low
Exploit odds (30 days)0.3%top 79.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 products (as reported)

VendorProductVersions
basecamp once-campfire < 1.4.5

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

References