CVE-2026-27959 - Vulnerability Analysis

Overview

Koa < 3.1.2 and < 2.16.4 contain a host header injection caused by naive parsing of HTTP Host header in ctx.hostname API, letting attackers inject attacker-controlled hostnames, exploit requires sending malformed Host header.

Severity & Score

Impact

Attackers can inject arbitrary hostnames, potentially leading to phishing, URL spoofing, or bypassing security checks.

Mitigation

Upgrade to versions 3.1.2 or 2.16.4 or later.

References

• https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df
• https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb
• https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm

Social Media Activity(1 post)

TheHackerWire

@thehackerwire

Feb 26, 2026

🟠 CVE-2026-27959 - High (7.5) 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 conf... 🔗 https://www.thehackerwire.com/vulnerability/CVE-2026-27959/ #CVE #vulnerability #infosec #cybersecurity #security #Tenda #patchstack

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