css_parser 1.22.0/2.0/2.1.0 on Ruby Parser#read_remote_file server-side request forgery

Summaryinfo

A vulnerability classified as critical has been found in css_parser on Ruby. The impacted element is the function CssParser::Parser#read_remote_file. Performing a manipulation results in server-side request forgery. This vulnerability is cataloged as CVE-2026-53727. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in css_parser on Ruby. It has been classified as critical. This affects the function CssParser::Parser#read_remote_file. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. 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. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-53727. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 327779 (Linux Distros Unpatched Vulnerability : CVE-2026-53727), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.0.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (327779). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Ruby Gem

Name

• css_parser

Version

• 1.22.0
• 2.0
• 2.1.0

CPE 2.3info

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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