CVE-2026-22037
Path encoding bypass lets bypass middleware in @fastify/express <4.0.3
Is CVE-2026-22037 being exploited?
Not confirmed. CVE-2026-22037 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 0.36% probability of exploitation in the next 30 days.
How severe is CVE-2026-22037?
CVE-2026-22037 is rated High with a CVSS score of 8.4. 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-2026-22037?
Yes. A fix has been recorded for CVE-2026-22037. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-22037 affect?
CVE-2026-22037 affects npm @fastify/express <4.0.3. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-22037?
Upgrade to 4.0.3+; verify route protections
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Encoded path bypasses middleware; attackers access protected endpoints without required constraints
Patch when possible
- affected< 4.0.3
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.