CVE-2026-27959
7.5 HIGHKoa is middleware for Node.js using ES2017 async functions
Published: 2026-02-26 · Last updated: 2026-06-16
Severity and scoring
- CVSS
- 7.5 HIGH
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CWE
- CWE-20
Affected products
| Vendor | Product |
|---|---|
| koajs | koa |
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.
Source: NVD
References
- [NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-27959
- [Patch]https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df
- [Patch]https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb
- [Vendor advisory]https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm
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