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MEDIUM severity

GHSA-qp7p-654g-cw7p — hono

MEDIUM

GHSA-qp7p-654g-cw7p is a medium-severity (CVSS 4.3) CWE-74 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.

Hono has CSS Declaration Injection via Style Object Values in JSX SSR

Also known asCVE-2026-44458
Published
May 9, 2026
Updated
Sep 10, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-qp7p-654g-cw7p.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs24th percentile — riskier than 24% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

How urgent is this, really

GHSA-qp7p-654g-cw7p plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.

Where this sits among everything scored

Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

6Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream
hononpm
46.1Mdownloads / week

Description

Summary

The JSX renderer escapes style attribute object values for HTML but not for CSS. Untrusted input in a style object value or property name can therefore inject additional CSS declarations into the rendered style attribute. The impact is limited to CSS and does not allow JavaScript execution or HTML attribute breakout.

Details

style object values are serialized into a CSS declaration list and escaped for HTML attribute context only. Characters that act as CSS declaration boundaries — such as ;, comment markers, quoted strings, and block delimiters — are valid in HTML attribute content and can extend a value beyond its assigned property.

This issue arises when untrusted input is interpolated into a JSX style object and rendered server-side.

Impact

An attacker who can control the value or property name of a style object may inject arbitrary CSS declarations. This may lead to:

  • Visual manipulation of the page, including full-viewport overlays usable for phishing
  • Outbound requests to attacker-controlled hosts via CSS resource references such as url(...)
  • Hijacking of UI affordances through layout, positioning, or visibility changes

This issue affects applications that render JSX on the server with style object values or property names derived from untrusted input.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmhonoall versions4.12.18npm install hono@4.12.18

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update hono to 4.12.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qp7p-654g-cw7p is resolved across your whole dependency graph.

  3. 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.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-qp7p-654g-cw7p can be triaged on real exposure rather than presence alone.

Tailored to GHSA-qp7p-654g-cw7p. 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 JSX renderer escapes `style` attribute object values for HTML but not for CSS. Untrusted input in a `style` object value or property name can therefore inject additional CSS declarations into the rendered `style` attribute. The impact is limited to CSS and does not allow JavaScript execution or HTML attribute breakout. ### Details `style` object values are serialized into a CSS declaration list and escaped for HTML attribute context only. Characters that act as CSS declaration boundaries — such as `;`, comment markers, quoted strings, and block delimiters — are valid in HTML
O3 Security · Impact-Aware SCA

Is GHSA-qp7p-654g-cw7p in your dependencies?

O3 Security finds GHSA-qp7p-654g-cw7p across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

GHSA-qp7p-654g-cw7p: hono (Medium 4.3) | O3 Security