CVE-2026-47675: Hono Cookie Helper Does Not Sanitize Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3hrh-pfw6-9m5x",
  "modified" : "2026-06-04T17:59:25Z",
  "published" : "2026-06-04T17:59:25Z",
  "aliases" : [ "CVE-2026-47675" ],
  "summary" : "Hono: Cookie helper does not sanitize sameSite and priority, allowing Set-Cookie injection",
  "details" : "### Summary\n\nThe `serialize()` function in `hono/cookie` validates `domain` and `path` options against characters that corrupt `Set-Cookie` header syntax (`;`, `\\r`, `\\n`), but does not apply the same validation to `sameSite` and `priority`. An application that passes user-controlled input into either option may produce a `Set-Cookie` response header containing attacker-chosen additional attributes.\n\n### Details\n\nWhen constructing a `Set-Cookie` header value, `serialize()` appends the `sameSite` and `priority` option values directly into the output string after a presentation-only transformation (capitalizing the first character). Although the TypeScript type signature constrains these options to specific string literals, that constraint is not enforced at runtime; any string value, including one containing `;` or line-feed characters, passes through unchanged.\n\nThe validation guard that rejects `;`, `\\r`, and `\\n` from `domain` and `path` is not applied to `sameSite` or `priority`. An application that passes a request-derived value to either option therefore provides an injection point into the header line.\n\nThis issue arises when an application passes user-controlled input to the `sameSite` or `priority` option of `setCookie()` or `serialize()`.\n\n### Impact\n\nAn attacker who can control the `sameSite` or `priority` option value may inject additional attributes into a `Set-Cookie` response header.\n\nThis may lead to:\n\n- Cookie attribute injection — overriding `Domain`, `Path`, `HttpOnly`, `Secure`, or `Max-Age` for the affected cookie\n- HTTP response header injection on runtimes that do not strictly validate header values, enabling a second attacker-controlled `Set-Cookie` header in the same response\n\nThis issue affects applications that pass user-derived input into the `sameSite` or `priority` option of `hono/cookie` serialization functions.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.12.21"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-3hrh-pfw6-9m5x"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-47675"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/905aedbc20661e0e2fa378783a7ec44a5c3df43d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.12.21"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-113", "CWE-1287" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-04T17:59:25Z",
    "nvd_published_at" : "2026-05-28T17:16:32Z"
  }
}