CVE-2026-27601
DoS via stack overflow in Underscore.js _.flatten/.isEqual (<1.13.8).
Is CVE-2026-27601 being exploited?
Not confirmed. CVE-2026-27601 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 0.96% probability of exploitation in the next 30 days.
How severe is CVE-2026-27601?
CVE-2026-27601 is rated High with a CVSS score of 8.2. 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-2026-27601?
Yes. A fix has been recorded for CVE-2026-27601. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-27601 affect?
CVE-2026-27601 affects Underscore.js (<1.13.8). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-27601?
Upgrade to 1.13.8+
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
DoS via stack overflow when processing deeply nested data with untrusted input through _.flatten or _.isEqual.
Patch when possible
- affected< 1.13.8
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.