CVE-2020-15270 is a medium-severity (CVSS 4.3) CWE-672 vulnerability in parse-server. A fix is available for parse-server — see the affected versions and patch details below.
receiving subscription objects with deleted session
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-15270 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
parse-servernpmDescription
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | parse-server | all versions | 4.4.0npm install parse-server@4.4.0 |
Affected Products
parse-serverparseplatformDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for parse-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update parse-server to 4.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15270 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.
Frequently Asked Questions
Is CVE-2020-15270 in your dependencies?
Find it across npm, including transitive dependencies.