CVE-2026-39408
ADVISORY - githubSummary
Summary
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.
Details
The static site generation process creates output files based on route paths derived from application routes and parameters. When ssgParams is used to provide values for dynamic routes, those values are used to construct output file paths. If these values contain traversal sequences (e.g. ..), the resulting output path may resolve outside the configured output directory. As a result, files may be written to unintended locations instead of being confined within the specified output directory.
For example:
import { Hono } from 'hono'
import { toSSG, ssgParams } from 'hono/ssg'
const app = new Hono()
app.get('/:id', ssgParams([{ id: '../pwned' }]), (c) => {
return c.text('pwned')
})
toSSG(app, fs, { dir: './static' })
In this case, the generated output path may resolve outside ./static, resulting in a file being written outside the intended output directory.
Impact
An attacker who can influence values passed to ssgParams during the build process may be able to write files outside the intended output directory.
Depending on the build and deployment environment, this may:
- overwrite unintended files
- affect generated artifacts
- impact deployment outputs or downstream tooling
This issue is limited to build-time static site generation and does not affect request-time routing.
GitHub
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CVSS SCORE
5.9medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| hono | npm | - | - | >=4.0.0,<=4.12.11 | 4.12.12 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is not bound to the network stack and the attacker's path is via read/write/execute capabilities. Either: The attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
A successful attack depends on conditions beyond the attacker's control, requiring investing a measurable amount of effort in research, preparation, or execution against the vulnerable component before a successful attack.
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is no loss of confidentiality within the Vulnerable System.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Vulnerable System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is no impact to availability within the Vulnerable System.
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
NIST
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CVSS SCORE
5.9mediumChainguard
CGA-hg64-9r55-fh6m
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minimos
MINI-3324-w2w9-v95f
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