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

Source: https://junglewise.ai/threats/cve-2026-69207-hono-redos-in-cors-middleware-via-access-control-request-headers  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-07. Updated: 2026-08-03  
License: CC BY 4.0 with a link back

CVE-2026-69207 · Severity: medium · CVSS 5.3 · Published 2026-08-07

A vulnerability in the Hono web framework's CORS middleware can allow an attacker to crash or slow down a web service. By sending a specially crafted request with a long sequence of spaces in the headers, an attacker can force the server to consume excessive CPU power. This can lead to a denial-of-service, making the application unavailable to legitimate users.

Technologies: [hono (npm)](https://junglewise.ai/threats/technologies/hono). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-69207 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-69207 being exploited in the wild.

**How severe is CVE-2026-69207?** Medium severity, with a CVSS score of 5.3, published 7 August 2026.

**Which products and versions are affected?** hono (npm) < 4.12.34, SEMVER:introduced=0,fixed=4.12.34.

**Is there a fix for CVE-2026-69207?** Yes. hono (npm): upgrade to 4.12.34 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-69207 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-69207?** Check whether you run hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- hono (npm): upgrade to 4.12.34 or later

  ```sh
  npm install hono@4.12.34
  ```


## Technical details

The Hono CORS middleware (`hono/cors`) uses a regular expression to parse the `Access-Control-Request-Headers` header during HTTP OPTIONS preflight requests. This regex exhibits quadratic backtracking (O(n²)) when processing long strings of whitespace without delimiters. An unauthenticated remote attacker can exploit this by sending a large header value, causing high CPU utilization and blocking the event loop in single-threaded runtimes. The vulnerability exists in the default configuration where `allowHeaders` is not explicitly defined. A fix is available in version 4.12.34.

## Affected products

- Hono Hono < 4.12.34

## Identifiers

- CVE-2026-69207
- GHSA-8j4g-w8fx-2239

## Timeline

- 2026-08-03: disclosed
- 2026-08-03: patched: Fixed in version 4.12.34
- 2026-08-03: advisory

## References

- [https://api.github.com/users/sonicnew](https://api.github.com/users/sonicnew)
- [https://github.com/sonicnew](https://github.com/sonicnew)
- [https://api.github.com/users/sonicnew/gists%7B/gist_id%7D](https://api.github.com/users/sonicnew/gists%7B/gist_id%7D)
- [https://api.github.com/users/sonicnew/repos](https://api.github.com/users/sonicnew/repos)
- [https://avatars.githubusercontent.com/u/173318515?v=4](https://avatars.githubusercontent.com/u/173318515?v=4)
- [https://api.github.com/users/sonicnew/events%7B/privacy%7D](https://api.github.com/users/sonicnew/events%7B/privacy%7D)

## Related threats

- [Hono: `css` helper does not escape a closing tag split between the template and an interpolated value, allowing HTML injection](https://junglewise.ai/threats/cve-2026-126359-hono-css-helper-does-not-escape-a-closing-tag-split-between-the)
- [Hono RegExpRouter middleware bypass via wildcard matching](https://junglewise.ai/threats/cve-2026-126358-hono-regexprouter-skips-wildcard-middleware-for-some-route-sets)
- [Hono mount() path traversal bypasses middleware scoping](https://junglewise.ai/threats/cve-2026-126357-hono-mount-and-app-mount-can-forward-a-path-that-bypasses)
- [Hono validator form multipart/form-data parameter bypass](https://junglewise.ai/threats/cve-2026-126356-hono-validator-form-skips-validation-for-multipart-form-data)
- [Hono csrf() middleware bypass via hyperlink auditing](https://junglewise.ai/threats/cve-2026-126355-hono-csrf-does-not-check-requests-sent-by-hyperlink-auditing)