{"id":"CVE-2026-59895","aliases":["GHSA-w62v-xxxg-mg59"],"url":"https://o3.security/vulnerability/CVE-2026-59895","summary":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","details":"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":"2026-07-08T16:09:51.273Z","modified":"2026-08-12T03:51:26.737993221Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"epss":{"score":0.00327,"percentile":0.25316,"asOf":"2026-09-05"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"hono","fixedVersion":"4.12.27"}],"fix":{"url":"https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc","label":"honojs/hono@cd3f6f7"},"references":[{"type":"WEB","url":"https://github.com/honojs/hono/releases/tag/v4.12.27"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59895.json"},{"type":"ADVISORY","url":"https://github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59895"},{"type":"FIX","url":"https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:26.737993221Z"}}