JumpServer is a popular open-source bastion host, which provides secure access to remote systems and helps to isolate internal networks from external threats. However, a recent vulnerability - CVE-2023-42820 - has been discovered that affects users of JumpServer. This vulnerability results from an issue where the random number seed used to generate verification codes is exposed to the API. Consequently, attackers can potentially replay these verification codes and reset passwords.

It is important to note that users with Multi-Factor Authentication (MFA) enabled or those not using local authentication are not affected by this vulnerability. The developers of JumpServer have recommended upgrading to either version 2.28.19 or 3.6.5 to mitigate this issue, as there are no known workarounds.

Here is a code snippet that demonstrates how the random number seed is exposed to the API

# JumpServer/settings.py
import random
random.seed(os.getenv("RANDOM_SEED", "some_random_string"))

# JumpServer/apps/users/utils.py
def generate_otp():
    return random.randint(100000, 999999)

As shown in the code above, the random seed is set in the settings.py file using the RANDOM_SEED environment variable. The generate_otp() function is then used to generate a random verification code using this seed, which becomes exposed to the API. An attacker could potentially use this exposed random number seed to replicate the verification codes and perform a replay attack for password resets, thereby gaining unauthorized access to user accounts.

In response to this vulnerability, the original developers of JumpServer have provided a solution by updating their software. The issue has been addressed in the following releases:

- JumpServer 2.28.19
- JumpServer 3.6.5

Users are strongly advised to upgrade their JumpServer instances to one of these versions to eliminate the risk that CVE-2023-42820 poses. In addition, enabling MFA and employing non-local authentication methods can further strengthen the security posture of your JumpServer deployment.

For more information about this vulnerability, please refer to the following resources

- Original JumpServer GitHub Repository
- JumpServer Release Notes
- CVE-2023-42820 Vulnerability Details

In conclusion, CVE-2023-42820 is a security vulnerability that affects JumpServer users by exposing the random number seed to the API and potentially allowing replay attacks for password resets. To protect your deployment, upgrade to JumpServer version 2.28.19 or 3.6.5, enable MFA, and use non-local authentication methods. Stay vigilant and stay secure!


Published on: 09/27/2023 15:19:00 UTC
Last modified on: 09/29/2023 15:04:00 UTC