How severe is CVE-2026-39408?

CVE-2026-39408 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 high, integrity none, and availability none.

Is CVE-2026-39408 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39408?

CVE-2026-39408 affects Hono. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39408?

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-2026-39408 have an EU (EUVD) identifier?

Yes. CVE-2026-39408 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20495.

When was CVE-2026-39408 published?

CVE-2026-39408 was published on 2026-04-08 and last updated on 2026-06-17.

CVE-2026-39408

CVE-2026-39408 is a high-severity vulnerability in Hono 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-22.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 5.9
EPSS exploit prediction: 1% (41st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-20495
Weakness: CWE-22
Affected product: Hono
Published: 2026-04-08
Last modified: 2026-06-17

Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path traversal issue in toSSG() allows files to be written outside the configured output directory during static site generation. When using dynamic route parameters via ssgParams, specially crafted values can cause generated file paths to escape the intended output directory. This vulnerability is fixed in 4.12.12.

Frequently asked questions

What is CVE-2026-39408?: Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path traversal issue in toSSG() allows files to be written outside the configured output directory during static site generation. When using dynamic route parameters via ssgParams, specially crafted values can cause generated file paths to escape the intended output directory. This vulnerability is fixed in 4.12.12.
How severe is CVE-2026-39408?: CVE-2026-39408 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 high, integrity none, and availability none.
Is CVE-2026-39408 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39408?: CVE-2026-39408 affects Hono. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39408?: 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-2026-39408 have an EU (EUVD) identifier?: Yes. CVE-2026-39408 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20495.
When was CVE-2026-39408 published?: CVE-2026-39408 was published on 2026-04-08 and last updated on 2026-06-17.

References

Affected products (1)

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

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