{"id":"CVE-2026-59895","aliases":["CLSA-2026-1793790161","EUVD-2026-42327","GHSA-w62v-xxxg-mg59","ROOT-APP-NPM-CVE-2026-59895"],"status":"published","title":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","description":"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.","severity":{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00327,"percentile":0.2602,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-116","CWE-79"],"published":"2026-07-08T16:09:51Z","modified":"2026-11-04T14:45:06Z","fixes":[{"ecosystem":"npm","package":"hono","fixed_in":["4.12.27"],"sources":["ghsa","osv"]},{"ecosystem":"TuxCare:npm","package":"hono","fixed_in":["3.12.12-tuxcare.5"],"sources":["osv"]},{"ecosystem":"Root:npm","package":"hono","fixed_in":["4.12.25-aikido.1"],"sources":["osv"]},{"ecosystem":"Root:npm","package":"@rootio/hono","fixed_in":["4.12.25-root.io.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.12.27"}]}]},{"source":"osv","ecosystem":"TuxCare:npm","package":"hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.12.12-tuxcare.0"},{"fixed":"3.12.12-tuxcare.5"}]}],"versions":["3.12.12","3.12.12-tuxcare.1","3.12.12-tuxcare.2","3.12.12-tuxcare.3","3.12.12-tuxcare.4"]},{"source":"osv","ecosystem":"npm","package":"hono","ranges":[{"type":"SEMVER","events":[{"introduced":"4.0.0"},{"fixed":"4.12.27"}]}]},{"source":"osv","ecosystem":"Root:npm","package":"hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.12.25-aikido.1"}]}]},{"source":"osv","ecosystem":"Root:npm","package":"@rootio/hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.12.25-root.io.1"}]}]}],"products":[{"vendor":"hono","product":"hono"},{"vendor":"honojs","product":"hono"}],"references":[{"url":"https://github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59","tags":["x_refsource_CONFIRM","Vendor Advisory","advisory","web"]},{"url":"https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/honojs/hono/releases/tag/v4.12.27","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59895","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-w62v-xxxg-mg59"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59895.json","tags":["advisory"]},{"url":"https://github.com/honojs/hono","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-59895","title":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","description":"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.","status":"published","published":"2026-07-08T16:09:51.273Z","modified":"2026-07-08T19:41:04.292Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-79","CWE-116"],"updated_at":"2026-11-02T14:19:58.560602Z"}],"euvd":[{"id":"EUVD-2026-42327","description":"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.","status":"published","published":"2026-07-08T16:09:51Z","modified":"2026-07-08T19:41:04Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T18:20:10.095263Z"}],"ghsa":[{"id":"GHSA-w62v-xxxg-mg59","title":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","description":"### Summary\n\n`cx()` in `hono/css` composes class names from plain strings but marks the result as already-escaped without HTML-escaping the input. When the result is used as a JSX `class` attribute during server-side rendering, the value is written into the attribute unescaped, so untrusted input can break out of the `class` attribute and inject arbitrary markup, leading to Cross-Site Scripting (XSS).\n\n### Details\n\nBecause the composed value is treated as pre-escaped, the HTML attribute escaping normally applied to interpolated values is skipped, and characters such as `\"` pass through unescaped — allowing a value to terminate the attribute and add further attributes or elements. This arises when an application passes untrusted, user-controlled input as a class name to `cx()`, for example when merging a base class with an externally provided `className`.\n\n### Impact\n\nDuring server-side rendering, an attacker who controls a value passed to `cx()` can inject arbitrary HTML into the page, resulting in stored or reflected XSS in the victim's browser.\n\nThis may lead to:\n\n- Execution of attacker-controlled script in the victim's browser session.\n- Session hijacking, credential theft, or actions performed on behalf of the victim.\n\nApplications are affected only if they render JSX server-side and pass untrusted input as a class name to `cx()`.","status":"published","published":"2026-07-21T18:33:50Z","modified":"2026-07-21T18:33:50Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-79","CWE-116"],"updated_at":"2026-11-02T14:40:50.444681Z"}],"nvd":[{"id":"CVE-2026-59895","description":"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.","status":"published","published":"2026-07-08T17:17:27.353Z","modified":"2026-10-25T17:10:00.197Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-79","CWE-116"],"updated_at":"2026-11-02T14:12:28.040501Z"}],"osv":[{"id":"CVE-2026-59895","title":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","description":"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.","status":"published","published":"2026-07-08T16:09:51.273Z","modified":"2026-10-28T02:30:35.559935508Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-116","CWE-79"],"updated_at":"2026-11-02T15:45:12.496548Z"},{"id":"GHSA-w62v-xxxg-mg59","title":"Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility","description":"### Summary\n\n`cx()` in `hono/css` composes class names from plain strings but marks the result as already-escaped without HTML-escaping the input. When the result is used as a JSX `class` attribute during server-side rendering, the value is written into the attribute unescaped, so untrusted input can break out of the `class` attribute and inject arbitrary markup, leading to Cross-Site Scripting (XSS).\n\n### Details\n\nBecause the composed value is treated as pre-escaped, the HTML attribute escaping normally applied to interpolated values is skipped, and characters such as `\"` pass through unescaped — allowing a value to terminate the attribute and add further attributes or elements. This arises when an application passes untrusted, user-controlled input as a class name to `cx()`, for example when merging a base class with an externally provided `className`.\n\n### Impact\n\nDuring server-side rendering, an attacker who controls a value passed to `cx()` can inject arbitrary HTML into the page, resulting in stored or reflected XSS in the victim's browser.\n\nThis may lead to:\n\n- Execution of attacker-controlled script in the victim's browser session.\n- Session hijacking, credential theft, or actions performed on behalf of the victim.\n\nApplications are affected only if they render JSX server-side and pass untrusted input as a class name to `cx()`.","status":"published","published":"2026-07-21T18:33:50Z","modified":"2026-09-10T03:51:12.371507758Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-116","CWE-79"],"updated_at":"2026-11-02T15:46:58.04805Z"},{"id":"CLSA-2026-1793790161","title":"TuxCare security update for hono (1 CVE)","description":"TuxCare rebuilt hono to address 1 CVE. Fixed in 3.12.12-tuxcare.5.","status":"published","published":"2026-11-04T12:02:42Z","modified":"2026-11-04T14:45:06.150464578Z","updated_at":"2026-11-04T15:03:54.132276Z"},{"id":"ROOT-APP-NPM-CVE-2026-59895","title":"CVE-2026-59895 in hono - Patched by Root","description":"Root has patched CVE-2026-59895 in the hono package for Root:npm. Multiple fixed versions available.","status":"published","published":"2026-09-25T06:19:53Z","modified":"2026-09-25T07:15:22.277927295Z","updated_at":"2026-11-02T15:53:27.649662Z"}]}}