CVE-2026-27959Koa is middleware for Node.js using ES2017 async functions.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-20
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
koajs koa koajs:koa | before 2.16.4; from 3.0.0 before 3.1.2 | NVD |
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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.