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VulnerabilityPublished

CVE-2026-47676: honojs hono · HTTP Request/Response Smuggling

Affects honojs honoSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.12.21 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
5.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 4.12.21
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 28 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade hono and honojs/hono to 4.12.21.

Affected software

ProductAffectedFixed in
honojshonoAffected
  • <4.12.21
Fixed in
  • 4.12.21
npmhonojs/honopkg:npm/honojs/honoOther threatsAffected
  • <4.12.21
Fixed in
  • 4.12.21

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade honojs hono to version 4.12.21 or later, where this vulnerability is fixed. Since the vendor has released a fixed version, applying this official update is the recommended remediation. Patch status is confirmed by the version fix note. No additional mitigation guidance or temporary workarounds are provided.

Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, app.mount() strips the mount prefix from the incoming request path using the raw URL pathname, while route matching is performed against the percent-decoded path. This inconsistency causes the prefix to be stripped at the wrong position when the path contains percent-encoded multi-byte characters, resulting in the mounted sub-application receiving an incorrect path. This vulnerability is fixed in 4.12.21.

References

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