CVE-2026-21887 OpenCTI has a Semi-Blind SSRF via Unvalidated External URL in Data Ingestion Feature
Attackers can exploit unvalidated URLs in data ingestion to perform semi-blind SSRF attacks against internal services.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-21887?
CVE-2026-21887 is a high-severity server-side request forgery vulnerability in OpenCTI-Platform opencti, published on 12 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
OpenCTI is an open source platform for managing cyber threat intelligence knowledge and observables. Prior to 6.8.16, 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. This vulnerability is fixed in 6.8.16.
Weakness: CWE-918
Which versions are affected by CVE-2026-21887?
3 open source packages ship an affected version, including pycti. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pycti PyPI | All versions | 6.8.16 |
pycti PyPI | All versions | 6.8.16 |
pycti PyPI | All versions | 6.8.16 |
Products include Citeum Opencti.
How do I fix CVE-2026-21887?
Upgrade pycti to 6.8.16 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-21887 being exploited?
There is no known exploitation of CVE-2026-21887 in the wild and no public exploit code.
Other vulnerabilities in OpenCTI-Platform opencti
- CVE-2026-27960 OpenCTI privilege escalation and unauthenticated access via default admin account
- CVE-2026-39980 OpenCTI affected by RCE via notifier template
- CVE-2025-24977 OpenCTI has remote code execution and sensitive secrets exposed through web hook
- CVE-2024-26139 OpenCTI Authenticated Privilege Escalation
- CVE-2024-45404 OpenCTI's lack of Rate Limit lead to OTP brute forcing
Sources
Also known as GHSA-ffm6-vvph-g5f5, PYSEC-2026-118.