CVE-2026-85239
Fix: MISP/MISP@a90d552CVE-2026-85239 is a Improper Input Validation vulnerability. O3 Security confirms whether CVE-2026-85239 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
A vulnerability in MISP's event template handling allowed an authenticated user with permission to create or modify event templates to bypass validation of the template definition field. The…
Description
A vulnerability in MISP's event template handling allowed an authenticated user with permission to create or modify event templates to bypass validation of the template definition field.
The EventTemplate::beforeValidate() method only performed semantic validation when the supplied definition was already represented as an array. If a caller instead supplied a pre-encoded string, including malformed JSON or JSON representing an unexpected data type, the value bypassed validateDefinition() and only needed to satisfy the generic notBlank validation rule. As a result, an invalid event template definition could be stored persistently in the database.
When event templates were subsequently retrieved, EventTemplate::afterFind() attempted to decode the stored definition using JsonTool::decode() without handling decoding failures. A definition containing invalid JSON could therefore trigger an exception during retrieval. Because the event template index is available to all authenticated users, a single malicious or malformed template could make the event template listing and other functionality relying on EventTemplate queries return HTTP 500 errors until the offending database row was manually repaired.
Valid JSON representing an unexpected type, rather than the expected JSON object, could similarly result in invalid data reaching downstream consumers.
The vulnerability can therefore be exploited by a user capable of saving event templates to persist malformed template data and cause a persistent denial of service against event-template functionality for other users.
The patch enforces that event template definitions must be supplied as structured objects before saving and always applies semantic validation. On retrieval, malformed JSON and definitions that do not decode to the expected structure are caught, logged, and replaced with an empty definition, preventing a malformed database entry from breaking all event template queries.
Poisoning doesn't seem reachable according to the lead developer.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-85239 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-85239 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-85239. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-85239 in your dependencies?
O3 detects CVE-2026-85239 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.