CVE-2026-44214
MEDIUMCVE-2026-44214 is a medium-severity (CVSS 5.8) CWE-93 vulnerability in eventsource-encoder. O3 Security confirms whether CVE-2026-44214 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
eventsource-encoder: SSE event injection via unsanitized event and id fields
Real-World Exposure
eventsource-encoderReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
eventsource-encoder encodes events as well-formed EventSource/Server Sent Event (SSE) messages. Prior to 1.0.2, eventsource-encoder does not sanitize the event or id fields of an EventSourceMessage before serializing them. An attacker who controls either field can inject arbitrary Server-Sent Events line terminators (\n, \r, or \r\n) and thereby forge additional SSE fields or entire messages on the stream. This vulnerability is fixed in 1.0.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | eventsource-encoder | all versions | 1.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for eventsource-encoder. 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.
Fix
Update eventsource-encoder to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44214 is resolved across your whole dependency graph.
Workarounds
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-2026-44214 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-2026-44214. 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-2026-44214 in your dependencies?
O3 detects CVE-2026-44214 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.