CVE-2025-59043

JSON objects after decoding might use more memory than their serialized version. It is possible to tune a JSON to maximize the factor between serialized memory usage and deserialized memory usage (similar to a zip bomb). While reproducing the issue, we could reach a factor of about 35. This can be used to circumvent the [max_request_size (https://openbao.org/docs/configuration/listener/tcp/) configuration parameter, which is meant to protect against Denial of Service attacks, and also makes Denial of Service attacks easier in general, as the attacker needs much less resources.

Details

The request body is parsed into a map[string]interface{} https://github.com/openbao/openbao/blob/788536bd3e10818a7b4fb00aac6affc23388e5a9/http/logical.go#L50 very early in the request handling chain (before authentication), which means an attacker can send a specifically crafted JSON object and cause an OOM crash. Additionally, for simpler requests with large numbers of strings, the audit subsystem can consume large quantities of CPU.

To remediate, set max_request_json_memory and max_request_json_strings.

Resources

This issue was disclosed directly to HashiCorp and is the OpenBao equivalent of the following tickets:

• https://discuss.hashicorp.com/t/hcsec-2025-24-vault-denial-of-service-though-complex-json-payloads/76393
• https://nvd.nist.gov/vuln/detail/CVE-2025-6203

HashiCorp attributes the problem to the audit subsystem. For OpenBao, it was noted the problem was additionally in the requests handling logic.

• Unauthenticated Denial of Service

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2025-59043 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.1); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-59043? CVE-2025-59043 is a high-severity uncontrolled resource consumption vulnerability in github.com/openbao/openbao (go), affecting versions <= 2.4.0. It is fixed in 2.4.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2025-59043? CVE-2025-59043 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/openbao/openbao are affected by CVE-2025-59043? github.com/openbao/openbao (go) versions <= 2.4.0 is affected.
4. Is there a fix for CVE-2025-59043? Yes. CVE-2025-59043 is fixed in 2.4.1. Upgrade to this version or later.
5. Is CVE-2025-59043 exploitable, and should I be worried? Whether CVE-2025-59043 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-59043 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-59043? Upgrade github.com/openbao/openbao to 2.4.1 or later.