CVE-2026-39410CWE-20

Hono has a non-breaking space prefix bypass in cookie name handling in getCookie()

Medium · published April 8, 2026

CVSS v3.1
4.8
EPSS
0%
Percentile
25.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.8 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00332 · 25.3th percentile
Weakness
CWE-20 · Improper Input Validation
Published
2026-04-08T14:44Z
EPSS history
Timeline
  • 08 APR 14:44Z
    Hono has a non-breaking space prefix bypass in cookie name handling in getCookie()
    cvelistv5