CVE-2026-59895
CVE-2026-59895 — Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility
Hono is a Web application framework that provides support for any JavaScript runtime. From 4.0.0 before 4.12.27, cx() in hono/css composes class names from plain strings but marks the result as already escaped without HTML-escaping the input, allowing untrusted className values used in a JSX class attribute during server-side rendering to break out of the attribute and inject arbitrary markup. This issue is fixed in version 4.12.27.
Published Updated Sources: cvelistV5, GitHub_M
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
0%
chance of exploitation in 30 days
CVSS base
6.1
MEDIUM
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script all four kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Vendors (1)
Products (1)
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 6.1 | CVSS 3.1 | MEDIUM | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-79
- CWE-116
Detection
Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.
- Search application, proxy, and WAF logs for requests touching /css.
References
3 on the record
- github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59
x_refsource_CONFIRM
- github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc
x_refsource_MISC
- github.com/honojs/hono/releases/tag/v4.12.27
x_refsource_MISC
Elsewhere on this site
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.