{"id":"CVE-2026-44458","aliases":["GHSA-qp7p-654g-cw7p"],"url":"https://o3.security/vulnerability/CVE-2026-44458","summary":"Hono: CSS Declaration Injection via Style Object Values in JSX SSR","details":"### Summary\n\nThe 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.\n\n### Details\n\n`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.\n\nThis issue arises when untrusted input is interpolated into a JSX `style` object and rendered server-side.\n\n### Impact\n\nAn attacker who can control the value or property name of a `style` object may inject arbitrary CSS declarations. This may lead to:\n\n- Visual manipulation of the page, including full-viewport overlays usable for phishing\n- Outbound requests to attacker-controlled hosts via CSS resource references such as `url(...)`\n- Hijacking of UI affordances through layout, positioning, or visibility changes\n\nThis issue affects applications that render JSX on the server with `style` object values or property names derived from untrusted input.","published":"2026-05-13T15:01:37.198Z","modified":"2026-08-12T03:51:28.696450934Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"},"epss":{"score":0.00197,"percentile":0.09463,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"hono","fixedVersion":"4.12.18"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44458.json"},{"type":"ADVISORY","url":"https://github.com/honojs/hono/security/advisories/GHSA-qp7p-654g-cw7p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44458"},{"type":"PACKAGE","url":"https://github.com/honojs/hono"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:28.696450934Z"}}