CVE-2026-39408: Hono is a Web application framework that provides support for any JavaScript runtime

Q: How do I fix CVE-2026-39408?

hono: upgrade to newer than 4.12.11. Exact commands for each OS are on this page.

Q: Is CVE-2026-39408 being exploited?

CVE-2026-39408 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-39408 affect?

CVE-2026-39408 affects hono. Severity is high (CVSS 7.5). 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

Q: How urgent is CVE-2026-39408?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-39408 is a high-severity flaw (CVSS 7.5) affecting hono. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-22
Published	2026-04-08
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: hono

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-08 15:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

hono hono UPGRADE

Affected: >= 4.0.0 and <= 4.12.11

Fixed in: newer than 4.12.11

Safe to downgrade to: a release before 4.0.0

1. Check installed version

npm ls hono

2. UPGRADE to newer than 4.12.11

npm install hono@">4.12.11"

3. If no update is available yet, DOWNGRADE to a release before 4.0.0

npm view hono versions npm install hono@"<4.0.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39408?

hono: upgrade to newer than 4.12.11. Exact commands for each OS are on this page.

Is CVE-2026-39408 being exploited?

CVE-2026-39408 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39408 affect?

CVE-2026-39408 affects hono. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-39408?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-44456 MEDIUM 6.5 UPGRADE Hono is a Web application framework that provides support for any JavaScript runtime
CVE-2026-44457 MEDIUM 5.3 UPGRADE Hono is a Web application framework that provides support for any JavaScript runtime
CVE-2026-44455 MEDIUM 4.7 UPGRADE Hono is a Web application framework that provides support for any JavaScript runtime
CVE-2026-44458 MEDIUM 4.3 UPGRADE Hono is a Web application framework that provides support for any JavaScript runtime
CVE-2026-44459 LOW 3.8 UPGRADE Hono is a Web application framework that provides support for any JavaScript runtime

References

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