CVE-2026-29086

CVE-2026-29086 is a medium-severity vulnerability in Hono with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1113.

Key facts

Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, the setCookie() utility did not validate semicolons (;), carriage returns (\r), or newline characters (\n) in the domain and path options when constructing the Set-Cookie header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.

Frequently asked questions

What is CVE-2026-29086?
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, the setCookie() utility did not validate semicolons (;), carriage returns (\r), or newline characters (\n) in the domain and path options when constructing the Set-Cookie header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.
How severe is CVE-2026-29086?
CVE-2026-29086 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-29086 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-29086?
CVE-2026-29086 affects Hono. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-29086?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-29086 have an EU (EUVD) identifier?
Yes. CVE-2026-29086 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9508.
When was CVE-2026-29086 published?
CVE-2026-29086 was published on 2026-03-04 and last updated on 2026-06-17.

References

Affected products (1)

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