GHSA-79qm-7rj5-m7r9 CVE-2026-71849
Hono: Proxy Helper does not remove response headers listed in the `Connection` header
- Severity
- 3.7 / 10
- Low · CVSS 3.1
- Exploit chance (EPSS)
- 0.36%
- Chance of exploitation in the next 30 days. Higher than 29.20% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
- Fix
4.12.34- Upgrade hono to this version or later
Description
Summary
The Proxy Helper (hono/proxy) does not remove response headers named by the origin's Connection header. Headers that the origin marked as connection-scoped are therefore forwarded to clients.
Details
Per RFC 9110 Section 7.6.1, an intermediary must remove the header fields listed in a message's Connection header field before forwarding the message, in addition to the well-known hop-by-hop headers. The proxy() function removed the well-known hop-by-hop headers (including Connection itself) from origin responses, but did not remove the headers that the response's Connection header field designated as connection-scoped.
This issue arises when an application proxies responses from an origin that declares additional, non-standard headers as hop-by-hop via the Connection response header.
Impact
A client may receive response headers that the origin intended only for its immediate peer. This may lead to:
- Disclosure of connection-scoped or internal metadata contained in such headers
This issue affects applications that use the Proxy Helper (hono/proxy) to forward responses from origins that list custom header names in their Connection response header. Applications whose origins only use the standard hop-by-hop headers are not affected.
Affected versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| hono | >= 4.7.0, < 4.12.34 |
4.12.34 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
hono npm → 4.12.34
- npm
npm install hono@4.12.34- yarn
yarn add hono@4.12.34- pnpm
pnpm add hono@4.12.34
Severity breakdown
CVSS 3.1 3.7
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
How to prevent it
- Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-5r4p-p66f-jhc7 Hono: `serveStatic` decodes the request path a second time, leading to bypass of middleware on static paths | Medium | Also affects hono |
| GHSA-hxh3-vqpv-xpqv hono/jsx renders plain strings unescaped in boundary components, leading to XSS | Low | Also affects hono |
| GHSA-gqvv-2mrq-wpjv Hono: Incomplete fix for CVE-2026-39408: `toSSG()` still writes files outside the output directory | Medium | Also affects hono |
| GHSA-g6gw-c38x-mqfc Hono: Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion | Medium | Also affects hono |
| GHSA-crvj-82cr-hjcx Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials | Medium | Also affects hono |
| GHSA-f23p-vx2j-j53r Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure | Medium | Also affects hono |
| GHSA-54fx-42gc-7vw4 Hono: Algorithmic Complexity DoS in Language Middleware | Medium | Also affects hono |
| GHSA-8j4g-w8fx-2239 Hono: ReDoS in CORS middleware via Access-Control-Request-Headers | Medium | Also affects hono |
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