Koa has Host Header Injection via `ctx.hostname` (koajs koa)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.39 % · percentile 33 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Modified
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.
Weaknesses (CWE)
- CWE-20 — Improper Input Validation
References
- https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm
- https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df
- https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb
- https://access.redhat.com/security/cve/CVE-2026-27959
- https://bugzilla.redhat.com/show_bug.cgi?id=2442928
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27959.json
- https://access.redhat.com/errata/RHSA-2026:10184
- https://access.redhat.com/errata/RHSA-2026:7249
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | GitHub_M |
| CVSS 3.1 | HIGH 8.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N | redhat-SADP |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | HIGH 8.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N | NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary) |
Advisories
- GHSA-7gcc-r8m5-44qm — Koa has Host Header Injection via ctx.hostname
European references
- ENISA EUVD · EUVD-2026-8816
- GCVE · GCVE-0-2026-27959
CERT-FR advisories
- CERTFR-2026-AVI-1056 — Multiples vulnérabilités dans les produits Splunk · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:koajs:koa:*:*:*:*:*:node.js:*:*< 2.16.4cpe:2.3:a:koajs:koa:*:*:*:*:*:node.js:*:*≥ 3.0.0 < 3.1.2
Affected products
| Product | Versions |
|---|---|
| koajs · koa | affected >= 3.0.0, < 3.1.2 ; affected < 2.16.4 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |