CVE-2026-44458
Hono: CSS Declaration Injection via Style Object Values in JSX SSR
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.18, 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. This vulnerability is fixed in 4.12.18.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Hono: CSS Declaration Injection via Style Object Values in JSX SSR
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.18, 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. This vulnerability is fixed in 4.12.18.
- Record
CVE-2026-44458- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Weakness
- CWE-74, CWE-116
- Updated
- 2026-11-02
EUVDEUVD-2026-30037
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.18, 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. This vulnerability is fixed in 4.12.18.
- Record
EUVD-2026-30037- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-qp7p-654g-cw7p
Hono has CSS Declaration Injection via Style Object Values in JSX SSR
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.
- Record
GHSA-qp7p-654g-cw7p- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Weakness
- CWE-74, CWE-116
- Updated
- 2026-11-02
NVD
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.18, 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. This vulnerability is fixed in 4.12.18.
- Record
CVE-2026-44458- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Weakness
- CWE-74, CWE-116
- Updated
- 2026-11-02
OSV
Hono: CSS Declaration Injection via Style Object Values in JSX SSR
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.18, 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. This vulnerability is fixed in 4.12.18.
- Record
CVE-2026-44458- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Weakness
- CWE-116, CWE-74
- Updated
- 2026-11-02
OSVGHSA-qp7p-654g-cw7p
Hono has CSS Declaration Injection via Style Object Values in JSX SSR
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.
- Record
GHSA-qp7p-654g-cw7p- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Weakness
- CWE-116, CWE-74
- Updated
- 2026-11-02
OSVROOT-APP-NPM-CVE-2026-44458
CVE-2026-44458 in @rootio/hono - Patched by Root
Root has patched CVE-2026-44458 in the @rootio/hono package for Root:npm. Multiple fixed versions available.
- Record
ROOT-APP-NPM-CVE-2026-44458- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
OSVCLSA-2026-1790597695 No score
TuxCare security update for hono (12 CVEs)
TuxCare rebuilt hono to address 12 CVEs. Fixed in 3.12.12-tuxcare.2.
- Record
CLSA-2026-1790597695- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
hononpm |
before 4.12.18 | 4.12.18 |
honoTuxCare:npm From an advisory covering 11 CVEs |
3.12.12-tuxcare.0 up to 3.12.12-tuxcare.2, plus listed versions 3.12.123.12.12-tuxcare.1 |
3.12.12-tuxcare.2 |
@rootio/honoRoot:npm |
before 4.12.14-root.io.3 | 4.12.14-root.io.34.12.14-root.io.14.12.14-root.io.24.12.14-root.io.44.12.14-root.io.54.12.14-root.io.64.12.14-root.io.74.12.14-root.io.84.12.12-root.io.2 |
honoRoot:npm |
before 4.12.14-aikido.3 | 4.12.14-aikido.34.12.14-aikido.44.12.14-aikido.54.12.14-aikido.64.12.14-aikido.74.12.14-aikido.84.12.12-aikido.2 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-44458 is a medium vulnerability (CVSS 4.3) in Hono, published May 9, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.20%, the 9th percentile. Fixed in hono 4.12.18.