Improper input validation in Hono
CVE-2026-39410
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a discrepancy between browser cookie parsing and parse() handling allows cookie prefix protections to be bypassed. Cookie names that are treated as distinct by the browser may be normalized to the same key by parse(), allowing attacker-controlled cookies to override legitimate ones. This vulnerability is fixed in 4.12.12.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.003 (20.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Hono
- Honojs Hono — versions < 4.12.12
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Third Party Advisory, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-39410?
- CVE-2026-39410 is a medium-severity vulnerability in Hono, classified under Improper Input Validation. CVSS score: 4.8/10. Published 2026-04-08.
- How severe is CVE-2026-39410?
- Medium severity. CVSS v3 base score is 4.8 out of 10.