CVE-2020-15270

Original Message:
Hi,

I create objects with one client with an ACL of all users with a specific column value. Thats working so far.

Then I deleted the session object from one user to look if he can receive subscription objects and he can receive them.
The client with the deleted session cant create new objects, which Parse restricts right.

The LiveQueryServer doesnt detect deleted sessions after the websocket connection was established.
There should be a mechanism that checks in an specific interval if the session exists.
I dont know if its true with expired sessions.

Any solutions?

Parse version: 4.3.0
Parse js SDK version: 2.17

Solution:
Hi guys.

I've found and fixed the problem. It happens because there are two caches in place for the session token:

• at Parse Server level, which, according with the docs, should be changed via cacheTTL option and defaults to 5 seconds;
• at Parse Live Query level, which, according with the docs, should be changed via liveQueryServerOptions.cacheTimeout and defaults to 30 days.

But there are three problems:

• cacheTTL has currently no effect over Live Query Server;
• cacheTimeout also has currently no effect over Live Query Server;
• cacheTimeout actually defaults to 1h.

So, currently, if you wait 1 hour after the session token was invalidated, the clients using the old session token are not able to receive the events.

What I did:

• Added a test case for the problem;
• Fixed cacheTTL for Live Query Server;
• Fixed cacheTimeout for Live Query Server;
• Changed the cacheTimeout to default 5s;
• Changed the docs to reflect the actual 5s default for cacheTimeout.

CVE-2020-15270 has a CVSS score of 4.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.4.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2020-15270? CVE-2020-15270 is a medium-severity security vulnerability in parse-server (npm), affecting versions < 4.4.0. It is fixed in 4.4.0.
2. How severe is CVE-2020-15270? CVE-2020-15270 has a CVSS score of 4.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of parse-server are affected by CVE-2020-15270? parse-server (npm) versions < 4.4.0 is affected.
4. Is there a fix for CVE-2020-15270? Yes. CVE-2020-15270 is fixed in 4.4.0. Upgrade to this version or later.
5. Is CVE-2020-15270 exploitable, and should I be worried? Whether CVE-2020-15270 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-15270 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-15270? Upgrade parse-server to 4.4.0 or later.

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