Hono: Cookie helper does not sanitize sameSite and priority, allowing Set-Cookie injection

published 2026-05-28 5 mo ago modified 2026-10-14 25 d ago also EUVD-2026-32925 , GHSA-3hrh-pfw6-9m5x

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits: 0; none known

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, the serialize() function in hono/cookie validates domain and path options against characters that corrupt Set-Cookie header syntax (;, \r, \n), but does not apply the same validation to sameSite and priority. An application that passes user-controlled input into either option may produce a Set-Cookie response header containing attacker-chosen additional attributes. This vulnerability is fixed in 4.12.21.

Patch / fix

fixed in 2 links 2

npm hono 4.12.21
hono hono 4.12.21

github.com/honojs/hono@905aedb commit
github.com/honojs/hono/releases/tag/v4.12.21 release

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 5 mo ago (2026-05-28)

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
GitHub	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	hono	<4.12.21	4.12.21

Affected products

honojs hono

Classification

Weakness

CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers
CWE-1287 Improper Validation of Specified Type of Input

References

github.com /honojs/hono/commit/905aedbc20661e0e2fa378783a7ec44a5c3df43d
web
github.com /honojs/hono/security/advisories/GHSA-3hrh-pfw6-9m5x
web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-47675
advisory
github.com /honojs/hono
package
github.com /honojs/hono/releases/tag/v4.12.21
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary