Medium severity · published Sep 1, 2026
CVE-2026-84364
Hono: Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion
5.3
CVSS
0.5%
EPSS
No
On KEV
Description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.5, when parseBody() expands dot-separated form field names into nested objects with dot-notation parsing enabled, it does not limit the nesting depth or the total number of intermediate objects created. Empty segments are preserved, so one deeply dotted field name can encode one nesting level per byte, while a large number of shallowly dotted fields can create the same amplification across a request. A request body within a normal size limit can therefore allocate an object graph far larger than the request after the body has already been accepted. An unauthenticated attacker who can reach an affected endpoint can send concurrent requests that exhaust the JavaScript heap, terminate the server process, and leave the service unavailable until restart. Dot-notation parsing is not enabled by default, and applications using the default behavior are not affected. This issue is fixed in version 4.13.5.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 45% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HO
hono · honojs
< 4.13.5 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84364
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-84364
github.com
https://github.com/honojs/hono/commit/531e9c5a3ae058d10de33f643055bd4009a87178
github.com
https://github.com/honojs/hono/releases/tag/v4.13.5
github.com
https://github.com/honojs/hono/security/advisories/GHSA-g6gw-c38x-mqfc
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