VulnerabilityAnalyzed

CVE-2026-39410

Prior to 4.12.12, a discrepancy between browser cookie parsing and parse() handling allows cookie prefix protections to be bypassed.

MEDIUM 4.8EPSS 0.28%

Does this matter?

Lower severity and a low EPSS score (0.28%). Track it; it rarely justifies an emergency change on its own.

Description

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.

CVSS 3.1: 4.8 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS: 0.28% probability · 21th percentile
CISA KEV: Not listed
Weakness: CWE-20
Affected: hono/hono
Source: security-advisories@github.com

References

https://github.com/honojs/hono/commit/cc067c85592415cb1880ad3c61ed923472452ec0Third Party Advisory
https://github.com/honojs/hono/releases/tag/v4.12.12Release Notes
https://github.com/honojs/hono/security/advisories/GHSA-r5rp-j6wh-rvv4Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.