CVE-2026-21887: Pycti OpenCTI Has Semi-Blind SSRF Vulnerability

HIGH
Advisory Identifier: GHSA-ffm6-vvph-g5f5
Share
CVSS 7.7
CWE-20 CWE-918
Published
Advisory Summary

CVE-2026-21887 is a HIGH (CVSS 7.7) opencti has semi-blind ssrf vulnerability (CWE-20: Improper Input Validation) affecting Pycti libraries in the PyPI ecosystem. The issue involves opencti has semi-blind ssrf via unvalidated external url in data ingestion feature. Remediation is available by upgrading affected packages to version 6.8.16.

CVE-2026-21887 at a Glance

CVE Identifier CVE-2026-21887
GHSA Identifier GHSA-ffm6-vvph-g5f5
Severity HIGH
CVSS v3.1 Base Score 7.7
CWE Classification CWE-20: Improper Input Validation
Affected Product Pycti
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-21887

To remediate this vulnerability, upgrade all affected Pycti dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pycti fixed: 6.8.16 
pip install pycti>=6.8.16
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pycti

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-21887, inspect your installed packages using pip:

pip show pycti

Analyze the terminal output to locate any version of Pycti in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.8.16), your application is affected.

Note: The pip show pycti command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Pycti, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary 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. ### Impact 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.

CVE-2026-21887 Affected Pycti Versions

1 component(s)
Fixed Versions:
6.8.16
Product / Package Ecosystem Affected Versions Fixed Version
pycti
pypi/pycti
PyPI
< 6.8.16
6.8.16

References

GitHub Advisory / Wiki ADVISORY
https://github.com/OpenCTI-Platform/opencti/security/advisories/GHSA-ffm6-vvph-g5f5
NVD — CVE-2026-21887 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21887
Pycti Source Repository REPOSITORY
https://github.com/OpenCTI-Platform/opencti
Pycti Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/pycti/PYSEC-2026-118.yaml

Frequently Asked Questions

What is CVE-2026-21887?
CVE-2026-21887 is a security vulnerability in Pycti involving OpenCTI has Semi-Blind SSRF via Unvalidated External URL in Data Ingestion Feature under CWE-20: Improper Input Validation.
Which Pycti versions are affected?
Affected versions include releases prior to 6.8.16 across affected packages: pycti.
What version fixes CVE-2026-21887?
Upgrading to 6.8.16 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pycti affected?
Yes, pycti is affected in releases prior to 6.8.16. Upgrade your dependency to 6.8.16 or later.
What is the CVSS score of CVE-2026-21887?
CVE-2026-21887 has a CVSS v3.1 base score of 7.7 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N.
What CWE is associated with CVE-2026-21887?
CVE-2026-21887 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check PyPI dependencies for CVE-2026-21887?
Run the dependency tree command: 'pip show pycti'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-ffm6-vvph-g5f5",
  "modified" : "2026-06-22T17:01:22Z",
  "published" : "2026-06-22T17:01:22Z",
  "aliases" : [ "CVE-2026-21887" ],
  "summary" : "OpenCTI has Semi-Blind SSRF via Unvalidated External URL in Data Ingestion Feature",
  "details" : "### Summary\nThe 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.\n\nThis results in a semi-blind SSRF, as responses may not be fully visible but can still impact internal systems.\n\n### Impact\nOpenCTI’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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pycti"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.8.16"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/OpenCTI-Platform/opencti/security/advisories/GHSA-ffm6-vvph-g5f5"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-21887"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/OpenCTI-Platform/opencti"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/pycti/PYSEC-2026-118.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-22T17:01:22Z",
    "nvd_published_at" : "2026-03-12T17:16:36Z"
  }
}