# CVE-2026-109955: Hono 4.12.4 before 4.13.11 Middleware Bypass via serveStatic Double Decoding

> Attackers can bypass authentication middleware in Hono by exploiting double path decoding in serveStatic, accessing protected static files without credentials.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Oct 2026
- **Updated:** 13 Oct 2026
- **Also known as:** GHSA-3g9q-qwv8-cxpf, RHSA-2026:84423, RHSA-2026:84431

## What is CVE-2026-109955?

CVE-2026-109955 is a medium-severity authentication bypass vulnerability in honojs hono, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Hono from 4.12.4 before 4.13.11 contains a middleware bypass vulnerability in serveStatic that allows unauthenticated attackers to skip prefix middleware by exploiting double path decoding. Attackers can send malformed percent-encoded paths that the router matches in encoded form, reaching static files without authentication checks running.

Weakness: CWE-174 (Double Decoding of the Same Data)

## Which versions are affected by CVE-2026-109955?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `grafana13.1` | Red Hat:hummingbird:1 | All versions | 0:13.1.7-0.2.hum1 |
| `grafana13.2` | Red Hat:hummingbird:1 | All versions | 0:13.2.3-0.2.hum1 |

## How do I fix CVE-2026-109955?

Upgrade to a fixed version.

## Is CVE-2026-109955 being exploited?

There is no known exploitation of CVE-2026-109955 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109955 and fix it if it is affected.

What it is: CVE-2026-109955 is a medium-severity authentication bypass vulnerability in honojs hono, published on 13 Oct 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-2026-109955 in the wild and no public exploit code.

Affected product: honojs hono. No package-level version data is available, so check the vendor advisory linked from the reference page.

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.
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-2026-109955/ (Markdown: https://insights.sbomify.com/CVE-2026-109955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109955
- OSV: https://osv.dev/vulnerability/CVE-2026-109955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109955/
Summaries are generated and may contain mistakes; the official description above is the record.