Unauthenticated RCE in libwebsockets (widely embedded websocket/HTTP libraries) with CVSS 9.8 — broad impact on apps, servers and IoT devices.
CVE-2026-19773
Unauthenticated HTTP/2 HPACK parsing RCE in libwebsockets (CVE-2026-19773)
Is CVE-2026-19773 being exploited?
Not confirmed. CVE-2026-19773 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.
How severe is CVE-2026-19773?
CVE-2026-19773 is rated Critical with a CVSS score of 9.8. 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-2026-19773?
Yes. A fix has been recorded for CVE-2026-19773. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-19773 affect?
CVE-2026-19773 affects libwebsockets, Applications linking libwebsockets, Servers exposing HTTP/2 via libwebsockets, Embedded/IoT devices using libwebsockets. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-19773?
Upgrade to the patched libwebsockets release or apply the upstream commit; if not possible, disable HTTP/2 and restrict access.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated out‑of‑bounds write in HTTP/2 HPACK path parsing enabling arbitrary code execution in the process.
Immediate action required
- affectedb4b5aed3903eaff09cd76a410f69bbe5dff66f8e
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.