CVE-2026-47675: hono HTTP Request/Response Splitting

Vulnerability summary

CVE-2026-47675 is a medium (CVSS 5.3) HTTP Request/Response Splitting vulnerability in hono. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.3% of scored vulnerabilities.

Timeline

1. 28-05-2026
   PublishedVulnerability first disclosed.
2. 28-05-2026
   Last modifiedVulnerability information updated.

Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, the serialize() function in hono/cookie validates domain and path options against characters that corrupt Set-Cookie header syntax (;, \r, \n), but does not apply the same validation to sameSite and priority. An application that passes user-controlled input into either option may produce a Set-Cookie response header containing attacker-chosen additional attributes. This vulnerability is fixed in 4.12.21.

• CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.
• CWE-1287Improper Validation of Specified Type of InputThe product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type.