4.8

CVE-2026-39410: hono Improper Input Validation

CVSS: 4.8v3.1MediumAnalyzed
AliasesCGA-4fx9-84hr-r9x2CGA-7x4f-8q3x-9g2wGHSA-r5rp-j6wh-rvv4
Published 08-04-2026Last modified 08-04-2026
Open JSON

Vulnerability summary

CVE-2026-39410 is a medium (CVSS 4.8) Improper Input Validation vulnerability in hono. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 25% of scored vulnerabilities.

Overall risk
19/100
0100
Low · default modelHow is this calculated?
CVSS score
4.8/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.33%
0%100%
Low · +0.05 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-6RR8-4MQX-6M62

Timeline

  1. 08-04-2026
    PublishedVulnerability first disclosed.
  2. 08-04-2026
    Last modifiedVulnerability information updated.

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 metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.33%

Chance of exploitation in the next 30 days

Percentile

25%

Versus all other CVEs

30-day change

+0.05 pp

From 0.28% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.33%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard20 products
  • gemini-cli< 0.37.0-r0
  • honoAll versions (No fix recorded)
  • hono-adapter-mqttAll versions (No fix recorded)
  • hono-cliAll versions (No fix recorded)
  • hono-compatAll versions (No fix recorded)
Hono1 product
Honojs1 product
Npm1 product
  • hono< 4.12.12
Wolfi1 product
  • langfuse-3-worker< 3.164.0-r5

5 vendors · 24 products

References

6 links