Affected: honojs hono

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.

Affected: npm: js-yaml

# Quadratic CPU consumption in `!!omap` resolution (js-yaml 3.x and 4.x)

## Summary

`resolveYamlOmap()` enforces key uniqueness for `!!omap` sequences with a linear scan (`objectKeys.indexOf(...)`) inside the per-element loop, making resolution **O(n²)** in the number of entries. A modestly sized YAML document therefore consumes disproportionate CPU inside `yaml.load()`, giving a denial of service against any consumer that parses untrusted YAML.

`!!omap` is registered in the **default schema** (`lib/schema/default.js` → `require('../type/omap')`), so a plain `yaml.load(untrustedInput)` with no options is affected — no custom schema or non-default configuration is required.

**This is the same weakness as CVE-2026-59870 / GHSA-724g-mxrg-4qvm**, which was fixed in the 5.x line in 5.2.1. That fix was never backported: both currently maintained legacy lines still carry the original implementation.

## Affected versions

| Line | Latest tested | Status | |---|---|---| | 3.x | **3.15.0** | Affected — `objectKeys.indexOf(pairKey)` at `lib/type/omap.js:29` | | 4.x | **4.3.0** | Affected — `objectKeys.indexOf(pairKey)` at `lib/type/omap.js:30` | | 5.x | 5.2.2 | **Not affected** — fixed in 5.2.1 (uses a `Set`) |

Both figures are the newest release of each line at the time of writing, so this is not a "you are on an old version" issue.

## Details

`lib/type/omap.js` (js-yaml 4.3.0):

```js if (objectKeys.indexOf(pairKey) === -1) objectKeys.push(pairKey) else return false ```

`obj…