Vulnerability in Hono
CVE-2026-27700
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (27.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 27.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
- Hono
- Honojs Hono — versions >= 4.12.0, < 4.12.2
Weakness classification (CWE)
References
- github.com/honojs/hono/security/advisories/GHSA-xh87-mx6m-69f3 (Vendor Advisory)
- github.com/honojs/hono/commit/41adbf56e252c04611f8972364ac0887ae07a4c7 (Patch)
- github.com/honojs/hono/releases/tag/v4.12.2 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-27700?
- CVE-2026-27700 is a high-severity vulnerability in Hono, classified under Authentication Bypass by Spoofing. CVSS score: 8.2/10. Published 2026-02-25.
- How severe is CVE-2026-27700?
- High severity. CVSS v3 base score is 8.2 out of 10.