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Description

Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.

PUBLISHED Reserved 2026-06-22 | Published 2026-07-11 | Updated 2026-07-14 | Assigner VulnCheck




MEDIUM: 6.3CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
MEDIUM: 4.8CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem types

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Product status

Default status
unaffected

Any version before 4.12.7
affected

4.12.7 (semver)
unaffected

Credits

0xkakash1 reporter

References

github.com/...s/hono/security/advisories/GHSA-v8w9-8mx6-g223 (GitHub Security Advisory (GHSA-v8w9-8mx6-g223)) vendor-advisory

www.vulncheck.com/...-proto-key-in-parsebody-with-dot-option (VulnCheck Advisory: Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option) third-party-advisory

cve.org (CVE-2026-56763)

nvd.nist.gov (CVE-2026-56763)

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