Quick answers
- Is This vulnerability exploited in the wild?
- No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
- How severe is This vulnerability?
- High severity, with a CVSS score of 7.5, published 25 August 2026.
- Which products and versions are affected?
- nokogiri (RubyGems) < 1.19.3.
- Is there a fix for This vulnerability?
- A patch was published on 2026-04-27: Version 1.19.3 released with fixes Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is This vulnerability attacked?
- It is attacked over the network.
- Am I affected?
- Check whether you run nokogiri (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability exists in Nokogiri's CSS selector tokenizer, which uses regular expressions to parse CSS selectors. Three distinct ReDoS vectors were identified: (1) string-literal tokenization on unterminated quoted-string input, (2) string-literal tokenization on hex-escape-rich input, and (3) identifier tokenization on hex-escape-rich input. These regexes exhibit exponential worst-case complexity due to excessive backtracking behavior. The affected public methods include Nokogiri::CSS.xpath_for, Node#css, Node#at_css, Searchable#search, and CSS::Parser#parse. Attack vectors require network accessibility (for applications that process user-supplied CSS selectors) and no authentication or privileges. Exploitation causes CPU exhaustion leading to denial of service. The vulnerability is fixed in Nokogiri version 1.19.3 and later. Workarounds include avoiding user-controlled input in CSS selectors and setting Regexp.timeout on Ruby 3.2+ or JRuby 9.4+.
Affected products
- sparklemotion Nokogiri < 1.19.3
Timeline
- 2026-04-27: disclosed
- 2026-04-27: patched: Version 1.19.3 released with fixes