CVE-2026-16231
hbs async-helper escaping bypass allows stored/reflected XSS in server-rendered pages.
Is CVE-2026-16231 being exploited?
Not confirmed. CVE-2026-16231 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 0.23% probability of exploitation in the next 30 days.
How severe is CVE-2026-16231?
CVE-2026-16231 is rated High with a CVSS score of 8.1. 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-2026-16231?
Yes. A fix has been recorded for CVE-2026-16231. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16231 affect?
CVE-2026-16231 affects hbs 2.1.0–4.2.1, Express/Handlebars Node.js web apps, Server-rendered pages using hbs.registerAsyncHelper. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16231?
Upgrade to hbs 4.3.0; sanitize inputs or use hbs.SafeString for intentional raw HTML.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker-controlled data in async helpers can inject arbitrary HTML/JS into pages, enabling stored/reflected XSS, session theft, or account takeover.
Patch when possible
- affected>= 2.1.0 and < 4.3.0
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.