VULNERABILITY INTELLIGENCE

CVE-2026-27959

CVSS score7.5 HIGH
EPSS probability0.39%
CISA KEVNot currently listed
Published2026-02-26
Last modified2026-07-15
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Description

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.

Weakness classification

  • security-advisories@github.com: CWE-20
  • nvd@nist.gov: NVD-CWE-noinfo
  • 0b0ca135-0b70-47e7-9f44-1890c2a1c46c: CWE-20

Primary references