How severe is GHSA-xgm2-5f3f-mvvc?

GHSA-xgm2-5f3f-mvvc has a CVSS score of 4.8/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-xgm2-5f3f-mvvc?

GHSA-xgm2-5f3f-mvvc affects the following packages: hono (npm). Ecosystems affected: npm.

How do I fix GHSA-xgm2-5f3f-mvvc?

Update hono to 4.12.27 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-xgm2-5f3f-mvvc is resolved across your whole dependency graph.

How do I detect GHSA-xgm2-5f3f-mvvc in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-xgm2-5f3f-mvvc if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-xgm2-5f3f-mvvc?

O3 pinpoints whether GHSA-xgm2-5f3f-mvvc is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-xgm2-5f3f-mvvc actively exploited in the wild?

No public exploit code has been indexed for GHSA-xgm2-5f3f-mvvc yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is GHSA-xgm2-5f3f-mvvc?

GHSA-xgm2-5f3f-mvvc is classified as CWE-348 (CWE-348). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-xgm2-5f3f-mvvc published, and has it been updated?

GHSA-xgm2-5f3f-mvvc was published on July 21, 2026 and was last updated on July 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

GHSA-xgm2-5f3f-mvvc

MEDIUM

Hono: API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication

Also known asCVE-2026-59897

Published

Jul 21, 2026

Updated

Jul 23, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

hononpm

52.7Mdownloads / week

Description

Summary

The AWS API Gateway v1 adapter can drop a distinct repeated request header value. When a header appears multiple times, the adapter de-duplicates values using a substring comparison instead of an exact match, so a value that is a substring of another value of the same header is omitted (for example, 203.0.113.1 is dropped when another value is 203.0.113.10).

Details

A repeated request header carries an ordered list of values. Middleware or application logic that depends on the complete list — such as IP restriction that walks the X-Forwarded-For chain, rate limiting, audit logging, or proxy-chain validation — can therefore receive incomplete data that differs from what the client actually sent.

This issue arises on deployments using the AWS API Gateway v1 adapter (the same pattern also affects the VPC Lattice adapter), for requests that contain the same header more than once.

Impact

An attacker can craft repeated header values so that one value is omitted before the application sees the request. Where a security or routing decision relies on the full chain, this can alter that decision.

This affects applications deployed through Hono's AWS API Gateway v1 (or VPC Lattice) adapter that rely on the complete set of repeated request header values.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`hono`	≥ 4.3.3&&< 4.12.27	4.12.27

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update hono to 4.12.27 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-xgm2-5f3f-mvvc is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-xgm2-5f3f-mvvc is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-xgm2-5f3f-mvvc. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary The AWS API Gateway v1 adapter can drop a distinct repeated request header value. When a header appears multiple times, the adapter de-duplicates values using a substring comparison instead of an exact match, so a value that is a substring of another value of the same header is omitted (for example, `203.0.113.1` is dropped when another value is `203.0.113.10`). ### Details A repeated request header carries an ordered list of values. Middleware or application logic that depends on the complete list — such as IP restriction that walks the `X-Forwarded-For` chain, rate limiting, a

O3 Security · Impact-Aware SCA

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