CVE-2026-53727

Description

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.

Severity (CVSS)

Weaknesses

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

Affected products

References

• https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855h (x_refsource_CONFIRM)
• https://github.com/premailer/css_parser/commit/7d2ddf0189cd54b54f378f59daefa10cb036e476 (x_refsource_MISC)
• https://github.com/premailer/css_parser/commit/e0a151458b2a801ae265ba420862ef8b1127b3ae (x_refsource_MISC)
• https://github.com/premailer/css_parser/releases/tag/v3.0.0 (x_refsource_MISC)