CVE-2026-53727 PUBLISHED

css_parser: SSRF and Local File Disclosure in `CssParser::Parser#read_remote_file`

Assigner: GitHub_M
Reserved: 10.06.2026 Published: 17.07.2026 Updated: 17.07.2026

css_parser is a Ruby CSS parser. From 2.2.0 until 3.0.0, CssParser::Parser#read_remote_file in lib/css_parser/parser.rb, and therefore load_uri! and the @import-following branch of add_block!, issued HTTP and HTTPS requests against any host, port, and URI without a scheme allowlist, host or IP filtering, or protection against link-local, loopback, or RFC-1918 addresses. Location: redirects were followed recursively back into the same function, which also serviced file:// URIs, so a single attacker-controlled HTTP redirect could upgrade the bug from SSRF to arbitrary local file disclosure. Any consumer of css_parser that hands it attacker-influenced CSS together with a base_uri: option is exposed. This issue is fixed in version 3.0.0.

Metrics

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
CVSS Score: 8.9

Product Status

Vendor premailer
Product css_parser
Versions
  • Version < 3.0.0 is affected

References

Problem Types

  • CWE-918: Server-Side Request Forgery (SSRF) CWE