How severe is CVE-2026-39409?

CVE-2026-39409 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2026-39409 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39409?

CVE-2026-39409 affects Hono. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39409?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-39409 have an EU (EUVD) identifier?

Yes. CVE-2026-39409 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20497.

When was CVE-2026-39409 published?

CVE-2026-39409 was published on 2026-04-08 and last updated on 2026-06-17.

CVE-2026-39409

CVE-2026-39409 is a medium-severity vulnerability in Hono with a CVSS 3.x base score of 5.3. 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-180.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v4: 6.3
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-20497
Weakness: CWE-180
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, ipRestriction() does not canonicalize IPv4-mapped IPv6 client addresses (e.g. ::ffff:127.0.0.1) before applying IPv4 allow or deny rules. In environments such as Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior. This vulnerability is fixed in 4.12.12.

Frequently asked questions

What is CVE-2026-39409?: Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, ipRestriction() does not canonicalize IPv4-mapped IPv6 client addresses (e.g. ::ffff:127.0.0.1) before applying IPv4 allow or deny rules. In environments such as Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior. This vulnerability is fixed in 4.12.12.
How severe is CVE-2026-39409?: CVE-2026-39409 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2026-39409 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39409?: CVE-2026-39409 affects Hono. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39409?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39409 have an EU (EUVD) identifier?: Yes. CVE-2026-39409 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20497.
When was CVE-2026-39409 published?: CVE-2026-39409 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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