# CVE-2026-126358: Hono: RegExpRouter skips wildcard middleware for some route sets and for paths with an encoded line terminator

> Unauthenticated clients can reach route handlers or not-found handlers without wildcard middleware in Hono apps using RegExpRouter with certain patterns.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Harmful if only installed:** No
- **Needs a specific call:** Yes (`RegExpRouter`)
- **Fix available:** Yes
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-h7mg-cq63-vhpq

## What is CVE-2026-126358?

CVE-2026-126358 is a medium-severity authentication bypass vulnerability in honojs hono, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Hono is a Web application framework that provides support for any JavaScript runtime. From 4.1.4 until 4.13.16, RegExpRouter can omit wildcard middleware in three version-specific cases: since 4.13.0, middleware using the explicit default parameter pattern in /api/:tenant{[^/]+}/admin/* is not applied to a route written as /api/:tenant/admin/:id; since 4.1.4, middleware on /admin/* is not applied to a route registered as /admin* for paths under /admin/; and since 4.4.0, a request path containing an encoded line terminator can reach the not-found handler without wildcard middleware. The default SmartRouter selects RegExpRouter for most applications, and the router's registration-time coverage calculation treated the first two matching pattern pairs as different while its compiled wildcard did not match line terminators in the third case. An unauthenticated client can reach a route handler or the not-found handler without authentication or authorization middleware registered on the wildcard path. TrieRouter, LinearRouter, and PatternRouter apply the middleware in the three described cases. This issue is fixed in version 4.13.16.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-126358?

1 open source package ship an affected version, including hono.

An affected version is only exploitable if your software calls RegExpRouter. Many projects that include it are not exposed.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hono` | npm | From 4.1.4 | 4.13.16 |

## How do I fix CVE-2026-126358?

Upgrade hono to 4.13.16 or later.

## Is CVE-2026-126358 being exploited?

There is no known exploitation of CVE-2026-126358 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126358 and fix it if it is affected.

What it is: CVE-2026-126358 is a medium-severity authentication bypass vulnerability in honojs hono, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-126358 in the wild and no public exploit code.
Exposure: An affected version is only exploitable if your software calls RegExpRouter. Many projects that include it are not exposed.

Affected packages and fixed versions:
- hono (npm): affected from 4.1.4; fixed in 4.13.16

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
   If an affected version is present, also search the code for calls to RegExpRouter and report whether any exist.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126358/ (Markdown: https://insights.sbomify.com/CVE-2026-126358/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126358
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126358
- OSV: https://osv.dev/vulnerability/CVE-2026-126358

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126358/
Summaries are generated and may contain mistakes; the official description above is the record.