{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4k:http4k-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.49.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T21:16:03Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nThe `HmacSha256` class contained two functions:\n- `hash(payload)` \u2014 a plain unkeyed SHA-256 digest. The `Hmac` prefix in the class name was misleading; this function has no key parameter, so it could never have been an HMAC.\n- `hmacSHA256(key, data)` \u2014 a properly keyed HMAC-SHA256.\n\nA reader who didn\u0027t engage with the function signature could in principle have assumed `HmacSha256.hash(payload)` was somehow keyed, but the absence of any key parameter made that misuse unlikely in practice.\n\n**Who is affected:** any downstream caller who read the class name and used `HmacSha256.hash` as a message authentication code without noticing it takes no key. **Verified at v6.47.2.0: zero internal misuse in http4k itself.** Both production usages of `HmacSha256.hash` (AWS SigV4 canonical-request hashing in `AwsSignatureV4Signer.kt` and `x-amz-content-sha256` in `awsExtensions.kt`) are AWS-spec-correct uses of plain SHA-256; every keyed `hmacSHA256(key, data)` call passes a real key. The advisory exists so any downstream caller relying on the misleadingly-named API knows to migrate.\n\n### Patches\n\nUpgrade to **6.49.0.0** or later. The fix introduces:\n- `Sha256.hash(input)` \u2014 unkeyed digest (the actual behaviour `HmacSha256.hash` provided).\n- `Sha256.hmac(key, input)` \u2014 keyed HMAC-SHA256 (the behaviour the name implied).\n\n`HmacSha256` is deprecated. Existing callers continue to work via deprecation shims; migrate to `Sha256.hash` or `Sha256.hmac` per intent.\n\n### Workarounds\n\nIf you cannot upgrade and you need a real HMAC-SHA256, use `javax.crypto.Mac.getInstance(\"HmacSHA256\")` with a `SecretKeySpec`. For an unkeyed SHA-256 digest, use `java.security.MessageDigest.getInstance(\"SHA-256\")`. The keyed `hmacSHA256(key, data)` was always correctly implemented and is safe to use as-is.\n\n### References\n\n- Fix release: [v6.49.0.0](https://github.com/http4k/http4k/releases/tag/6.49.0.0)\n- Background: [RFC 2104 \u2014 HMAC: Keyed-Hashing for Message Authentication](https://datatracker.ietf.org/doc/html/rfc2104)",
  "id": "GHSA-m4w9-hjfw-vwj4",
  "modified": "2026-06-19T21:16:03Z",
  "published": "2026-06-19T21:16:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/http4k/http4k/security/advisories/GHSA-m4w9-hjfw-vwj4"
    },
    {
      "type": "WEB",
      "url": "https://datatracker.ietf.org/doc/html/rfc2104"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/http4k/http4k"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4k/http4k/releases/tag/6.49.0.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "http4k: `HmacSha256.hash` (despite the `Hmac` naming) computed a plain unkeyed digest; clarified by deprecation in favour of `Sha256.hash` / `Sha256.hmac`"
}