CVE-2026-79770
Regex DoS in Nokogiri CSS tokenizer allows crafted selectors to crash apps
Is CVE-2026-79770 being exploited?
Not confirmed. CVE-2026-79770 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.28% probability of exploitation in the next 30 days.
How severe is CVE-2026-79770?
CVE-2026-79770 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-79770?
Yes. A fix has been recorded for CVE-2026-79770. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-79770 affect?
CVE-2026-79770 affects Nokogiri < 1.19.3, Ruby applications using Nokogiri, Web apps and scrapers using CSS selectors. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-79770?
Upgrade Nokogiri to >= 1.19.3 and validate/sanitize untrusted CSS selectors
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Denial of Service: crafted CSS selectors passed to Node#css/Node#at_css/Searchable#search trigger exponential regex backtracking, high CPU and outages.
Patch when possible
- affected< 1.19.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.