How severe is CVE-2026-33806?

CVE-2026-33806 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-33806 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33806?

CVE-2026-33806 affects Fastify. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33806?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-33806 have an EU (EUVD) identifier?

Yes. CVE-2026-33806 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22818.

When was CVE-2026-33806 published?

CVE-2026-33806 was published on 2026-04-15 and last updated on 2026-06-30.

CVE-2026-33806

CVE-2026-33806 is a high-severity vulnerability in Fastify with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1287.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (33rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-22818
Weakness: CWE-1287
Affected product: Fastify
Published: 2026-04-15
Last modified: 2026-06-30

Description

Impact: Fastify applications using schema.body.content for per-content-type body validation can have validation bypassed entirely by prepending a space to the Content-Type header. The body is still parsed correctly but schema validation is skipped. This is a regression introduced in fastify >= 5.3.2 by the fix for CVE-2025-32442 Patches: Upgrade to fastify v5.8.5 or later. Workarounds: None. Upgrade to the patched version.

Frequently asked questions

What is CVE-2026-33806?: Impact: Fastify applications using schema.body.content for per-content-type body validation can have validation bypassed entirely by prepending a space to the Content-Type header. The body is still parsed correctly but schema validation is skipped. This is a regression introduced in fastify >= 5.3.2 by the fix for CVE-2025-32442 Patches: Upgrade to fastify v5.8.5 or later. Workarounds: None. Upgrade to the patched version.
How severe is CVE-2026-33806?: CVE-2026-33806 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-33806 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33806?: CVE-2026-33806 affects Fastify. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33806?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-33806 have an EU (EUVD) identifier?: Yes. CVE-2026-33806 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22818.
When was CVE-2026-33806 published?: CVE-2026-33806 was published on 2026-04-15 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*

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