# Duplicate Advisory: Hono vulnerable to Vary Header Injection leading to potential CORS Bypass

Source: https://junglewise.ai/threats/duplicate-advisory-hono-vulnerable-to-vary-header-injection-leading-to-5d1c74c3  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-01  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 6.5 · Published 2026-07-01

## Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-q7jf-gf43-6x6p. This link is maintained to preserve external references.

## Original Description
Hono before 4.10.2 (fixed in 4.10.3) contains a flaw in its CORS middleware: when the origin is not set to "*", the middleware copies the Vary header from the incoming request into the response. Because Vary is a response header that should be managed by the server, an attacker can supply arbitrary Vary values that are reflected into the response, potentially causing cache key pollution and inconsistent CORS enforcement in environments that rely on shared caches or proxies.

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

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 6.5, published 1 July 2026.

**Which products and versions are affected?** hono (npm) < 4.10.3.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected?** 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.

## Affected products

- hono (npm) < 4.10.3

## 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)