Hono has CSS Declaration Injection via Style Object Values in JSX SSR (CVE-2026-44458) | HOL Guard CVE

Medium · CVSS 4.3CVE-2026-44458GHSA-QP7P-654G-CW7P

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

Answer in brief

CVE-2026-44458 records a Medium severity (CVSS 4.3) vulnerability in Hono has CSS Declaration Injection via Style Object Values in JSX SSR. The current sources do not mark it as known exploited. The current feed maps hono (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 9, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 4.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 4.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps hono (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
hononpm	>=0 <4.12.18	4.12.18

Recommended response

Check inventory. Check lockfiles and deployed manifests for hono.
Review the reported fix. Update hono to 4.12.18 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 9, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.