CVE-2026-50555: @angular/platform-server Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hqr9-c56f-3x7f",
  "modified" : "2026-07-15T22:05:58Z",
  "published" : "2026-06-15T17:20:30Z",
  "aliases" : [ "CVE-2026-50555" ],
  "summary" : "@angular/platform-server: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')",
  "details" : "A Cross-Site Scripting (XSS) vulnerability exists in `@angular/platform-server`'s DOM emulation dependency (`domino`) when serializing the content of raw-text elements (such as `<script>`, `<style>`, and `<iframe>`).\n\n`domino` supports escaping raw-text elements during serialization to prevent closing-tag breakout. However, a **Unicode index alignment bug** existed in this escaping logic.\n\nIn JavaScript, string lengths and character indices are calculated based on UTF-16 code units (where astral characters—such as emojis—occupy 2 code units / 4 bytes). If the bound dynamic text contained astral Unicode characters _before_ the closing tag (e.g. `</script>`, `</style>`, or `</iframe>`), the index offset calculation in `domino`'s replacement logic shifted.\n\nThis misalignment caused `domino` to fail to replace or escape the closing tag, leaving it raw and unescaped in the output HTML.\n\nAn attacker who controls the dynamic text can supply a payload containing both an astral Unicode character and a closing tag (e.g., `😀</iframe><script>alert(1)</script>`). When serialized on the server during SSR, the browser parses the unescaped closing tag, exits the raw-text context early, and executes the subsequent `<script>` block, leading to same-origin Cross-Site Scripting (XSS).\n\n### Impact\n\nThis vulnerability allows an attacker to perform same-origin Cross-Site Scripting (XSS) attacks against any user visiting an SSR-rendered page that binds user-controlled data inside raw-text elements. This can lead to session hijacking, credentials theft, unauthorized actions on behalf of users, and defacement.\n\n### Patched Versions\n\n- 22.0.0-rc.2\n- 21.2.16\n- 20.3.24\n- 19.2.25\n\n### Workarounds\n\nIf you cannot immediately update your dependencies, you can:\n\n- Avoid binding user-controlled values inside `<iframe>` or other raw-text elements.\n- Sanitize any user input placed inside raw-text elements to explicitly strip closing tags before passing it to the template.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@angular/platform-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "22.0.0-next.0"
      }, {
        "fixed" : "22.0.0-rc.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@angular/platform-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "21.0.0-next.0"
      }, {
        "fixed" : "21.2.16"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@angular/platform-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "20.0.0-next.0"
      }, {
        "fixed" : "20.3.24"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@angular/platform-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "19.0.0-next.0"
      }, {
        "fixed" : "19.2.25"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@angular/platform-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "18.2.14"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/angular/angular/security/advisories/GHSA-hqr9-c56f-3x7f"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-50555"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/angular/domino/pull/29"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/angular/angular"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-15T17:20:30Z",
    "nvd_published_at" : "2026-06-22T18:16:43Z"
  }
}