CVE-2026-33946
Session hijack of SSE stream in MCP Ruby SDK before v0.9.2
Is CVE-2026-33946 being exploited?
Not confirmed. CVE-2026-33946 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 0.46% probability of exploitation in the next 30 days.
How severe is CVE-2026-33946?
CVE-2026-33946 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-2026-33946?
Yes. A fix has been recorded for CVE-2026-33946. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-33946 affect?
CVE-2026-33946 affects MCP Ruby SDK (< v0.9.2), Model Context Protocol servers/clients. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-33946?
Upgrade to 0.9.2+ to apply fix
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker with a valid session ID can hijack the SSE stream and intercept real-time data.
Patch when possible
- affected< 0.9.2
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.