Serendipity before 2.6.0 contains a server-side request forgery vulnerability in the serendipity_url_allowed() filter that fails to block hex-encoded IPv4 addresses, IPv6 literals, and link-local ranges. Authenticated users with adminImagesAdd permission can bypass the filter using alternate address formats to request internal services and retrieve response bodies through the public uploads directory.
https://www.vulncheck.com/advisories/serendipity-before-ssrf-via-hex-ipv4-and-ipv6-addresses
https://github.com/s9y/Serendipity/security/advisories/GHSA-2m48-gjj5-5x86
Published: 2026-08-13
Updated: 2026-08-13
Base Score: 7.5
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:P/A:N
Severity: High
Base Score: 8.5
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Severity: High
Base Score: 8.4
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
Severity: High