CVE-2026-21887

OpenCTI has Semi-Blind SSRF via Unvalidated External URL in Data Ingestion Feature

The OpenCTI platform’s data ingestion feature accepts user-supplied URLs without validation and uses the Axios HTTP client with its default configuration (allowAbsoluteUrls: true). This allows attackers to craft requests to arbitrary endpoints, including internal services, because Axios will accept and process absolute URLs.

This results in a semi-blind SSRF, as responses may not be fully visible but can still impact internal systems.

OpenCTI’s data ingestion feature can allow an attacker to make the application send HTTP requests to arbitrary internal or external endpoints. This means an attacker could reach internal services that are not exposed publicly, such as Elasticsearch, Redis, or RabbitMQ, and potentially extract sensitive data or manipulate internal components. In cloud environments, the attacker could target metadata services like AWS, Azure, or GCP to obtain credentials and configuration details, which could lead to full compromise of the infrastructure. Even though the SSRF is semi-blind and the attacker may not see the full response, the ability to interact with internal services can enable enumeration, data exfiltration, and in some cases remote code execution if internal APIs expose dangerous functionality.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-21887 has a CVSS score of 7.7 (High). The vector is network-reachable, low 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 (6.8.16); upgrading removes the vulnerable code path.

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1. What is CVE-2026-21887? CVE-2026-21887 is a high-severity improper input validation vulnerability in pycti (pip), affecting versions < 6.8.16. It is fixed in 6.8.16. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-21887? CVE-2026-21887 has a CVSS score of 7.7 (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 pycti are affected by CVE-2026-21887? pycti (pip) versions < 6.8.16 is affected.
4. Is there a fix for CVE-2026-21887? Yes. CVE-2026-21887 is fixed in 6.8.16. Upgrade to this version or later.
5. Is CVE-2026-21887 exploitable, and should I be worried? Whether CVE-2026-21887 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-2026-21887 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-2026-21887? Upgrade pycti to 6.8.16 or later.

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