# CVE-2026-36721: bookcars authentication bypass via forged JWT in validateAccessToken

Source: https://junglewise.ai/threats/cve-2026-36721-bookcars-authentication-bypass-via-forged-jwt-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-09. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-36721 · Severity: info · Published 2026-06-09

Bookcars is a car rental management system. A security flaw in its authentication process allows unauthorized individuals to bypass login requirements by using forged digital identity tokens. This could lead to unauthorized access to the system, potentially exposing customer data or allowing malicious changes to rental bookings.

Technologies: [BookCars](https://junglewise.ai/threats/technologies/bookcars). Vendors: [BookCars](https://junglewise.ai/threats/vendors/bookcars).

## Quick answers

**Is CVE-2026-36721 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-36721 being exploited in the wild.

**How severe is CVE-2026-36721?** Informational severity, published 9 June 2026.

**Which products and versions are affected?** BookCars 8.3.

**Is there a fix for CVE-2026-36721?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-36721 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-36721?** Check whether you run BookCars 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.

## Technical details

The vulnerability exists within the 'validateAccessToken' function of bookcars v8.3 due to a failure to verify the cryptographic signatures of JSON Web Tokens (JWT). Because the application trusts the contents of the token without validating its integrity against a secret key, a remote, unauthenticated attacker can craft a malicious JWT with arbitrary claims (such as administrative user IDs). By presenting this forged token in the authentication header, the attacker can successfully bypass authentication mechanisms and gain unauthorized access to protected API endpoints and user sessions.

## Affected products

- bookcars bookcars 8.3

## Timeline

- 2026-06-09: disclosed: Initial disclosure and NVD publication

## References

- [https://github.com/CC-T-454455/Vulnerabilities/tree/master/bookcars/vulnerability-2](https://github.com/CC-T-454455/Vulnerabilities/tree/master/bookcars/vulnerability-2)

## Related threats

- [BookCars authentication bypass via forged JWT in social-sign-in](https://junglewise.ai/threats/cve-2026-36727-bookcars-authentication-bypass-via-forged-jwt-in-social-sign-in)
- [BookCars arbitrary file deletion via directory traversal in delete-temp-license](https://junglewise.ai/threats/cve-2026-36726-bookcars-arbitrary-file-deletion-via-directory-traversal-in)
- [BookCars unrestricted file rename in /api/create-user component](https://junglewise.ai/threats/cve-2026-36723-bookcars-unrestricted-file-rename-in-api-create-user-component)
- [BookCars arbitrary file upload in create-license and create-car-image API](https://junglewise.ai/threats/cve-2026-36722-bookcars-arbitrary-file-upload-in-create-license-and-create-car)
- [BookCars privilege escalation in update-user endpoint](https://junglewise.ai/threats/cve-2026-36720-bookcars-privilege-escalation-in-update-user-endpoint)