CVE-2026-39410
Hono has a non-breaking space prefix bypass in cookie name handling in getCookie()
4.8CVSSMEDIUM
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 Vector Breakdown
Exploitability
AV:NAttack VectorNetwork
AC:HAttack ComplexityHigh
PR:NPrivileges RequiredNone
UI:NUser InteractionNone
Scope
S:UScopeUnchanged
Impact
C:LConfidentialityLow
I:LIntegrityLow
A:NAvailabilityNone
Weaknesses
Affected Products
Attack Graph
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Exploitability
Official Patch Available
MITRE ATT&CK
1 technique Initial Access
References
Timeline
Published
Apr 8, 2026
Last Updated
Apr 21, 2026
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