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.
Weakness
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Ruby-css-parser | Ubuntu | upstream | * |
Related Attack Patterns
References
- https://github.com/premailer/css_parser/commit/7d2ddf0189cd54b54f378f59daefa10cb036e476
- https://github.com/premailer/css_parser/commit/e0a151458b2a801ae265ba420862ef8b1127b3ae
- https://github.com/premailer/css_parser/releases/tag/v3.0.0
- https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855h
- https://github.com/premailer/css_parser/security/advisories/GHSA-9pmc-p236-855h