What’s Vulnerable › Vulnerabilities

CVE-2026-27700: Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-25 · updated 2026-06-17
• Weakness: CWE-290

Description

Hono is a Web application framework that provides support for any JavaScript runtime. In versions 4.12.0 and 4.12.1, when using the AWS Lambda adapter (`hono/aws-lambda`) behind an Application Load Balancer (ALB), the `getConnInfo()` function incorrectly selected the first value from the `X-Forwarded-For` header. Because AWS ALB appends the real client IP address to the end of the `X-Forwarded-For` header, the first value can be attacker-controlled. This could allow IP-based access control mechanisms (such as the `ipRestriction` middleware) to be bypassed. Version 4.12.2 patches the issue.

Affected products

• honojs hono: from 4.12.0 before 4.12.2 — fixed in 4.12.2

How to fix

Upgrade to a fixed version: honojs hono 4.12.2. Check the vendor advisory for mitigations.

References

• https://github.com/honojs/hono/commit/41adbf56e252c04611f8972364ac0887ae07a4c7
• https://github.com/honojs/hono/releases/tag/v4.12.2
• https://github.com/honojs/hono/security/advisories/GHSA-xh87-mx6m-69f3

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