Parse Server has Regular Expression Denial of Service (ReDoS) via `$regex` query in LiveQuery
Impact
A malicious client can subscribe to a LiveQuery with a crafted $regex pattern that causes catastrophic backtracking, blocking the Node.js event loop. This makes the entire Parse Server unresponsive, affecting all clients. Any Parse Server deployment with LiveQuery enabled is affected. The attacker only needs the application ID and JavaScript key, both of which are public in client-side apps.
This only affects LiveQuery subscription matching, which evaluates regex in JavaScript on the Node.js event loop. Normal REST and GraphQL queries are not affected because their regex is evaluated by the database engine.
Patches
Regex evaluation in LiveQuery subscription matching now runs in an isolated VM context with a configurable timeout via a new Parse Server option `liveQuery.regexTimeout, with defaults 100 ms. A regex that exceeds the timeout is treated as non-matching.
The protection adds approximately 50 microseconds of overhead per regex evaluation. For most applications this is negligible, but it can add up if there is a very large number of LiveQuery subscriptions that use $regex on the same class. For example, 10,000 concurrent regex subscriptions would add approximately 500ms of processing time per object save event on that class. Set liveQuery.regexTimeout: 0 to disable the protection and use native regex evaluation without overhead.
Workarounds
Use the beforeSubscribe Cloud Code hook to reject any LiveQuery subscription that contains a $regex operator. Note that this also blocks the LiveQuery startsWith, endsWith, and contains query methods, as they use $regex internally.
// Repeat for each class that is used with LiveQuery
Parse.Cloud.beforeSubscribe('MyClass', request => {
const where = request.query._where || {};
for (const value of Object.values(where)) {
if (value?.$regex) {
throw new Parse.Error(Parse.Error.OPERATION_FORBIDDEN, '$regex not allowed in LiveQuery subscriptions');
}
}
});References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-mf3j-86qx-cq5j
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.0-alpha.14
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.11
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | parse-server | >= 9.0.0-alpha.1, < 9.5.0-alpha.14, < 8.6.11 | 9.5.0-alpha.14, 8.6.11 |
References
- https://github.com/parse-community/parse-server/security/advisories/GHSA-mf3j-86qx-cq5j
- https://nvd.nist.gov/vuln/detail/CVE-2026-30925
- https://github.com/parse-community/parse-server
- https://github.com/parse-community/parse-server/releases/tag/8.6.11
- https://github.com/parse-community/parse-server/releases/tag/9.5.0-alpha.14
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-1333- Platform
- npm
- Package
parse-server- Disclosed
- 10.03.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-mf3j-86qx-cq5j - CC BY 4.0
Vulnerability history: parse-server
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 116
- First → latest
- 06.2019 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 17
- High 49
- Medium 40
- Low 10
Disclosures per year
- 2019: 2
- 2020: 4
- 2021: 4
- 2022: 12
- 2023: 5
- 2024: 4
- 2025: 6
- 2026: 79
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Parse Server has Regular Expression Denial of Service (ReDoS) via `$regex` query in LiveQuery this entry
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