CVE-2026-42270 countly-server: Unauthenticated Denial of Service (DoS) via Unhandled Stream Exception
Unauthenticated attackers can crash the Countly server by sending crafted requests to image routes, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42270?
CVE-2026-42270 is a high-severity denial of service vulnerability in countly-server, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
countly-server is the server-side part of Countly, a product analytics solution. Prior to 24.05.50 and 25.03.44, star-rating/images/ and dashboards/images/screenshots/ are among public image and screenshot routes using the local fs storage backend that call getStream and pipe filesystem streams to HTTP responses without an error listener. An unauthenticated request containing a URL-encoded dot can make createReadStream open a directory, emit an asynchronous EISDIR error, and terminate the Node.js process as an unhandled exception, allowing repeated requests to keep the analytics API unavailable. The affected routes also include /appimages/*, /memberimages/*, and */screenshots/*. This issue is fixed in versions 24.05.50 and 25.03.44.
Weakness: CWE-248
Which versions are affected by CVE-2026-42270?
How do I fix CVE-2026-42270?
No fix has been published for CVE-2026-42270 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-2026-42270 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42270 exists.
Sources
Also known as GHSA-86cv-qwp9-jwp3.