# CVE-2026-49858: API Platform Core information disclosure in JSON:API and HAL normalizers

Source: https://junglewise.ai/threats/cve-2026-49858-api-platform-core-information-disclosure-in-json-api-and-hal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-01. Updated: 2026-07-10  
License: CC BY 4.0 with a link back

CVE-2026-49858 · Severity: medium · CVSS 5.9 · Published 2026-07-01

API Platform, a framework for building web APIs, contains a flaw where sensitive data fields might be leaked to unauthorized users. This occurs because the system incorrectly reuses cached data structures between different users' requests when using JSON:API or HAL formats. In certain high-performance server environments, a lower-privileged user could see the structure of data that should have been hidden by security rules.

Technologies: [api-platform/core (Packagist)](https://junglewise.ai/threats/technologies/api-platform-core). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2026-49858 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-49858 being exploited in the wild.

**How severe is CVE-2026-49858?** Medium severity, with a CVSS score of 5.9, published 1 July 2026.

**Which products and versions are affected?** API Platform HAL >= 4.0.0, < 4.1.29; >= 4.2.0, < 4.2.25; >= 4.3.0, < 4.3.8; API Platform JSON-API >= 4.0.0, < 4.1.29; >= 4.2.0, < 4.2.25; >= 4.3.0, < 4.3.8; api-platform/core (Packagist) ECOSYSTEM:introduced=2.6.0,fixed=4.1.29; api-platform/hal (Packagist) ECOSYSTEM:introduced=4.0.0,fixed=4.1.29; and 1 more.

**Is there a fix for CVE-2026-49858?** Yes. api-platform/core (Packagist): upgrade to 4.1.29 or later; api-platform/hal (Packagist): upgrade to 4.1.29 or later; api-platform/json-api (Packagist): upgrade to 4.1.29 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-49858 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-49858?** Check whether you run API Platform HAL, API Platform JSON-API, api-platform/core (Packagist) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- api-platform/core (Packagist): upgrade to 4.1.29 or later

  ```sh
  composer require api-platform/core:^4.1.29
  ```

- api-platform/hal (Packagist): upgrade to 4.1.29 or later

  ```sh
  composer require api-platform/hal:^4.1.29
  ```

- api-platform/json-api (Packagist): upgrade to 4.1.29 or later

  ```sh
  composer require api-platform/json-api:^4.1.29
  ```


## Technical details

The vulnerability exists in the ItemNormalizer for JSON:API and HAL formats within API Platform Core. The `componentsCache` arrays are keyed on `$context['cache_key']` without verifying if the cache key is safe for the current security context (missing `isCacheKeySafe` gate). Consequently, if a high-privileged user triggers a resource normalization, the resulting structure—including restricted attributes—is cached and may be served to a subsequent low-privileged user. This is primarily exploitable in long-running PHP runtimes (e.g., FrankenPHP, RoadRunner, Swoole) where the normalizer instance persists across requests. Patches are available in versions 4.1.29, 4.2.25, and 4.3.8.

## Affected products

- api-platform core >= 2.6.0, < 4.1.29; >= 4.2.0, < 4.2.25; >= 4.3.0, < 4.3.8
- api-platform json-api >= 4.0.0, < 4.1.29; >= 4.2.0, < 4.2.25; >= 4.3.0, < 4.3.8
- api-platform hal >= 4.0.0, < 4.1.29; >= 4.2.0, < 4.2.25; >= 4.3.0, < 4.3.8

## Identifiers

- CVE-2026-49858
- GHSA-pjhx-3c3w-9v23

## Timeline

- 2026-06-04: disclosed
- 2026-07-01: advisory: NVD publication date
- 2026-07-10: advisory: GitHub Advisory published

## References

- [https://api.github.com/users/tillmon](https://api.github.com/users/tillmon)
- [https://github.com/tillmon](https://github.com/tillmon)
- [https://api.github.com/users/tillmon/gists%7B/gist_id%7D](https://api.github.com/users/tillmon/gists%7B/gist_id%7D)
- [https://api.github.com/users/tillmon/repos](https://api.github.com/users/tillmon/repos)
- [https://avatars.githubusercontent.com/u/30534957?v=4](https://avatars.githubusercontent.com/u/30534957?v=4)
- [https://api.github.com/users/tillmon/events%7B/privacy%7D](https://api.github.com/users/tillmon/events%7B/privacy%7D)

## Related threats

- [API Platform Core type confusion in AbstractItemNormalizer](https://junglewise.ai/threats/cve-2026-54164-api-platform-core-type-confusion-in-abstractitemnormalizer)
- [GraphQL grant on a property might be cached with different objects](https://junglewise.ai/threats/cve-2025-31485-graphql-grant-on-a-property-might-be-cached-with-different)
- [GraphQL query operations security can be bypassed](https://junglewise.ai/threats/cve-2025-31481-graphql-query-operations-security-can-be-bypassed)
- [API Platform Core can leak exceptions message that may contain sensitive information](https://junglewise.ai/threats/cve-2023-47639-api-platform-core-can-leak-exceptions-message-that-may-contain)
- [API Platform Core does not call GraphQl securityAfterResolver](https://junglewise.ai/threats/cve-2025-23204-api-platform-core-does-not-call-graphql-securityafterresolver)