HTTP response splitting in hono - CVE-2026-56762
Published: July 24, 2026
Vulnerability identifier: #VU139307
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-56762
CWE-ID: CWE-113
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper neutralization of CRLF sequences in HTTP headers in setCookie(), serialize(), and serializeSigned() when generating Set-Cookie headers with a user-controlled cookie name. A remote attacker can supply a crafted cookie name containing invalid characters to cause a denial of service.
In tested modern runtimes, malformed Set-Cookie headers are rejected before being sent, and the reported header injection behavior could not be reproduced.
Affected software
hono
How to mitigate CVE-2026-56762
Install security update from vendor's website.
hono - update to 4.12.12