# CVE-2026-69207: Hono: ReDoS in CORS middleware via Access-Control-Request-Headers

> Attackers can cause denial of service in Hono applications by sending crafted preflight requests that trigger excessive CPU usage in the CORS middleware.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Aug 2026
- **Updated:** 10 Aug 2026
- **Also known as:** CLEANSTART-2026-JS09983, ECHO-4b53-f5bc-1b65, GHSA-8j4g-w8fx-2239, MINI-3992-723j-7fqp, MINI-5fmg-h7xv-jfg8, MINI-79mx-fjjc-xxwc, MINI-f74p-6xq6-g3jr, MINI-j7q9-vxx5-c5hx, MINI-m8h6-67q9-r23f, MINI-pww5-wqh2-62h8, MINI-q8vg-p9v9-35g5, MINI-xm97-hgcj-v3c9, MINI-xmw7-cpc3-45m3, MINI-xv32-qf8w-2v5q

## What is CVE-2026-69207?

CVE-2026-69207 is a medium-severity denial of service vulnerability in honojs hono, published on 7 Aug 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. Prior to 4.12.34, the built-in CORS middleware, hono/cors, is vulnerable to a regular expression denial of service (ReDoS). During a preflight OPTIONS request, the middleware parses the attacker-controlled Access-Control-Request-Headers header using a whitespace-tolerant regular expression whose backtracking makes its running time quadratic in the input length. Because the header value is bounded only by the deployment's maximum HTTP header size, a single preflight carrying a long run of whitespace can consume seconds of CPU and block request processing. On runtimes that share one execution thread across requests, this stalls concurrent requests as well, and repeated requests can render the service unresponsive. This affects the default configuration, since the vulnerable path is reached whenever cors() is used with an unset or empty allowHeaders. Applications that set a non-empty allowHeaders are not affected. This issue is fixed in version 4.12.34.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-69207?

2 open source packages ship an affected version, including hono.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hono` | npm | All versions | 4.12.34 |
| `hono` | npm | All versions | 4.12.34 |

## How do I fix CVE-2026-69207?

Upgrade hono to 4.12.34 or later.

## Is CVE-2026-69207 being exploited?

There is no known exploitation of CVE-2026-69207 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-69207 and fix it if it is affected.

What it is: CVE-2026-69207 is a medium-severity denial of service vulnerability in honojs hono, published on 7 Aug 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-2026-69207 in the wild and no public exploit code.

Affected packages and fixed versions:
- hono (npm): affected all versions; fixed in 4.12.34
- hono (npm): affected all versions; fixed in 4.12.34

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-2026-69207/ (Markdown: https://insights.sbomify.com/CVE-2026-69207/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-69207
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-69207
- OSV: https://osv.dev/vulnerability/CVE-2026-69207

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-69207/
Summaries are generated and may contain mistakes; the official description above is the record.