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.
Metrics
CVSS 3.1 7.5/10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| koajs | koa | >= 3.0.0, < 3.1.2; < 2.16.4 |
| Red Hat | Red Hat OpenShift AI 2.25 | — |
| Red Hat | Red Hat OpenShift AI 2.25 | — |
| Red Hat | Red Hat OpenShift Container Platform 4.19 | — |
| Red Hat | Red Hat Developer Hub | — |
| Red Hat | Red Hat OpenShift AI (RHOAI) | — |
| Red Hat | Red Hat OpenShift Dev Spaces | — |
| Red Hat | Self-service automation portal 2 | — |
References
- https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6dfPatch
- https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfebPatch
- https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qmExploit, Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:10184
- https://access.redhat.com/errata/RHSA-2026:7249
- 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
Timeline
- Published
- Feb 26, 2026
- Last modified
- Jul 15, 2026
- NVD status
- Modified