CVE-2026-76821 OpenCTI: User-Controlled ReDoS in JSON Ingestion Mapper
An authenticated user can cause a denial of service in OpenCTI by submitting a malicious regular expression in the JSON ingestion mapper.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-76821?
CVE-2026-76821 is a high-severity denial of service vulnerability in OpenCTI-Platform opencti, published on 15 Sep 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 7.260706.0, the JSON ingestion mapper's extractWithRegexp formula function compiled a user-supplied regular expression with the JavaScript RegExp engine in opencti-platform/opencti-graphql/src/parser/json-mapper.ts without validating its complexity. An authenticated user with JSON mapper creation permission could provide a catastrophically backtracking pattern and matching ingestion input, blocking the Node.js event loop and making the GraphQL API unavailable to all users. Scheduled ingestion could repeatedly execute the malicious mapper without additional attacker action, and recovery could require disabling the mapper and restarting the process. The issue affects availability and does not expose or modify data. This issue is fixed in version 7.260706.0.
Which versions are affected by CVE-2026-76821?
How do I fix CVE-2026-76821?
No fix has been published for CVE-2026-76821 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-76821 being exploited?
There is no known exploitation of CVE-2026-76821 in the wild and no public exploit code.
Sources
Also known as GHSA-7g3x-wc2m-9h9x.