FKIE_CVE-2026-27959

Vulnerability from fkie_nvd - Published: 2026-02-26 02:16 - Updated: 2026-02-28 00:55
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa's `ctx.hostname` API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed Host header containing a `@` symbol is received, `ctx.hostname` returns `evil[.]com` - an attacker-controlled value. Applications using `ctx.hostname` for URL generation, password reset links, email verification URLs, or routing decisions are vulnerable to Host header injection attacks. Versions 3.1.2 and 2.16.4 fix the issue.
References
security-advisories@github.comhttps://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6dfPatch
security-advisories@github.comhttps://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfebPatch
security-advisories@github.comhttps://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qmExploit, Vendor Advisory
Impacted products
Vendor Product Version
koajs koa *
koajs koa *
To clipboard 

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  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:koajs:koa:*:*:*:*:*:node.js:*:*",
              "matchCriteriaId": "47B8F313-898E-4B6D-936A-8F35AC7E7C20",
              "versionEndExcluding": "2.16.14",
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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa\u0027s `ctx.hostname` API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed Host header containing a `@` symbol is received, `ctx.hostname` returns `evil[.]com` - an attacker-controlled value. Applications using `ctx.hostname` for URL generation, password reset links, email verification URLs, or routing decisions are vulnerable to Host header injection attacks. Versions 3.1.2 and 2.16.4 fix the issue."
    }
  ],
  "id": "CVE-2026-27959",
  "lastModified": "2026-02-28T00:55:26.413",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
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  },
  "published": "2026-02-26T02:16:23.317",
  "references": [
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      "tags": [
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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