CVE-2026-48819 json
Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key
published 5mo ago modified 18d ago also EUVD-2026-45267 , GHSA-hhx9-57xq-r5rw
- cvss
- 4.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 19%
- public exploits
- 0
- none known
Summary
Hey API is an ecosystem for turning API specifications into production-ready code. Prior to 0.97.3, dist/clients/core/params.ts ships a runtime template copied into generated SDKs as params.gen.ts, and buildClientParams writes unknown slot-prefixed keys such as $body_, $headers_, $path_, and $query_ directly to the corresponding slot, allowing $query___proto__ alongside a legitimate q field to set params.query through params["query"]["__proto__"] = value, call Object.setPrototypeOf(params.query, value), and expose inherited attacker-controlled keys during for..in iteration. This issue is fixed in version 0.97.3.
Patch / fix
- npm @hey-api/openapi-ts 0.97.3
Is CVE-2026-48819 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 3mo ago
Exploit prediction
0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-11).
Exploits and checks
- github.com https://github.com/hey-api/hey-api/security/advisories/GHSA-hhx9-57xq-r5rw referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N |
| GitHub | 3.1 | 4.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | @hey-api/openapi-ts | <0.97.3 |
0.97.3 |
Affected products
- hey-api openapi-ts
Classification
- Weakness
-
- CWE-1321 Improperly Controlled Modification of Object Prototype Attributes
References
- github.com /hey-api/hey-api/commit/023909137a15eff9c0263d3bcd116140076b214f
- github.com /hey-api/hey-api/commit/da321a1529eb3c90d2109da870f514b915a60169
-
github.com
/hey-api/hey-api/security/advisories/GHSA-hhx9-57xq-r5rw
exploit, advisory
- github.com /hey-api/hey-api/releases/tag/%40hey-api%2Fopenapi-ts%400.97.3
-
github.com
/hey-api/openapi-ts/security/advisories/GHSA-hhx9-57xq-r5rw
web
-
github.com
/hey-api/openapi-ts
package
Sources
- CVE List CVE-2026-48819
- GitHub Advisory GHSA-hhx9-57xq-r5rw
- NVD CVE-2026-48819
- Maintainer advisory GHSA-hhx9-57xq-r5rw
Fencer Intel 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.
The maintainers of hey-api/hey-api published their own advisory on GitHub. Reviewed sources take precedence over it.