CVE-2026-84363Network attack vectorHinoki check available

Cache poisoning via post-fragment query parsing

Published Sep 1, 2026 · Updated Sep 2, 2026

An interpretation conflict in Hono before 4.13.5 allows remote attackers to inject hidden parameters through a literal URL fragment. The URL helpers scan past # for ?, while createCacheKey removes the fragment, so application behavior can depend on data omitted from the cache key. A runtime and intermediary must preserve the literal fragment; affected cached reflections can poison responses and produce stored cross-site scripting.

CVSS severity5.9
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

An interpretation conflict in Hono before 4.13.5 allows remote attackers to inject hidden parameters through a literal URL fragment. The URL helpers scan past # for ?, while createCacheKey removes the fragment, so application behavior can depend on data omitted from the cache key. A runtime and intermediary must preserve the literal fragment; affected cached reflections can poison responses and produce stored cross-site scripting.

The record

CVE
CVE-2026-84363
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
Hono
Product
Hono
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.13.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hono · Honoversion=< 4.13.5

Published CVSS scores

5.9GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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