Vulnerability · Published Oct 16, 2026 · Assigned by GitHub_M

CVE-2026-42270countly-server: Unauthenticated Denial of Service (DoS) via Unhandled Stream Exception

High 7.5

In plain English

A high-severity security flaw in countly-server from Countly. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 46% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 54.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
Countly	countly-server	< 24.05.50>= 25.03, < 25.03.44

Weakness: CWE-248 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/Countly/countly-server/security/advisories/GHSA-86cv-qwp9-jwp3 x_refsource_CONFIRM
https://github.com/Countly/countly-server/commit/72f19bc5161117fa02a224bf9f7316bf42dae58d x_refsource_MISC
https://github.com/Countly/countly-server/commit/f9ad31480f94ee3ccc0f12708c8804be9c803f95 x_refsource_MISC
https://github.com/Countly/countly-server/releases/tag/24.05.50 x_refsource_MISC
https://github.com/Countly/countly-server/releases/tag/25.03.44 x_refsource_MISC