GHSA-qm95-pgcg-qqfq
CRITICALInsufficient validation when decoding a Socket.IO packet
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
socket.io-parsernpmDescription
Due to improper type validation in the socket.io-parser library (which is used by the socket.io and socket.io-client packages to encode and decode Socket.IO packets), it is possible to overwrite the _placeholder object which allows an attacker to place references to functions at arbitrary places in the resulting query object.
Example:
const decoder = new Decoder();
decoder.on("decoded", (packet) => {
console.log(packet.data); // prints [ 'hello', [Function: splice] ]
})
decoder.add('51-["hello",{"_placeholder":true,"num":"splice"}]');
decoder.add(Buffer.from("world"));
This bubbles up in the socket.io package:
io.on("connection", (socket) => {
socket.on("hello", (val) => {
// here, "val" could be a function instead of a buffer
});
});
:warning: IMPORTANT NOTE :warning:
You need to make sure that the payload that you received from the client is actually a Buffer object:
io.on("connection", (socket) => {
socket.on("hello", (val) => {
if (!Buffer.isBuffer(val)) {
socket.disconnect();
return;
}
// ...
});
});
If that's already the case, then you are not impacted by this issue, and there is no way an attacker could make your server crash (or escalate privileges, ...).
Example of values that could be sent by a malicious user:
- a number that is out of bounds
Sample packet: 451-["hello",{"_placeholder":true,"num":10}]
io.on("connection", (socket) => {
socket.on("hello", (val) => {
// val is `undefined`
});
});
- a value that is not a number, like
undefined
Sample packet: 451-["hello",{"_placeholder":true,"num":undefined}]
io.on("connection", (socket) => {
socket.on("hello", (val) => {
// val is `undefined`
});
});
- a string that is part of the prototype of
Array, like "push"
Sample packet: 451-["hello",{"_placeholder":true,"num":"push"}]
io.on("connection", (socket) => {
socket.on("hello", (val) => {
// val is a reference to the "push" function
});
});
- a string that is part of the prototype of
Object, like "hasOwnProperty"
Sample packet: 451-["hello",{"_placeholder":true,"num":"hasOwnProperty"}]
io.on("connection", (socket) => {
socket.on("hello", (val) => {
// val is a reference to the "hasOwnProperty" function
});
});
This should be fixed by:
- https://github.com/socketio/socket.io-parser/commit/b5d0cb7dc56a0601a09b056beaeeb0e43b160050, included in
[email protected] - https://github.com/socketio/socket.io-parser/commit/b559f050ee02bd90bd853b9823f8de7fa94a80d4, included in
[email protected] - https://github.com/socketio/socket.io-parser/commit/04d23cecafe1b859fb03e0cbf6ba3b74dff56d14, included in
[email protected] - https://github.com/socketio/socket.io-parser/commit/fb21e422fc193b34347395a33e0f625bebc09983, included in
[email protected]
Dependency analysis for the socket.io package
socket.io version | socket.io-parser version | Covered? |
|---|---|---|
4.5.2...latest | ~4.2.0 (ref) | Yes :heavy_check_mark: |
4.1.3...4.5.1 | ~4.0.4 (ref) | Yes :heavy_check_mark: |
3.0.5...4.1.2 | ~4.0.3 (ref) | Yes :heavy_check_mark: |
3.0.0...3.0.4 | ~4.0.1 (ref) | Yes :heavy_check_mark: |
2.3.0...2.5.0 | ~3.4.0 (ref) | Yes :heavy_check_mark: |
Dependency analysis for the socket.io-client package
socket.io-client version | socket.io-parser version | Covered? |
|---|---|---|
4.5.0...latest | ~4.2.0 (ref) | Yes :heavy_check_mark: |
4.3.0...4.4.1 | ~4.1.1 (ref) | No, but the impact is very limited |
3.1.0...4.2.0 | ~4.0.4 (ref) | Yes :heavy_check_mark: |
3.0.5 | ~4.0.3 (ref) | Yes :heavy_check_mark: |
3.0.0...3.0.4 | ~4.0.1 (ref) | Yes :heavy_check_mark: |
2.2.0...2.5.0 | ~3.3.0 (ref) | Yes :heavy_check_mark: |
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | socket.io-parser | ≥ 4.0.0&&< 4.0.5 | 4.0.5 |
| 📦npm | socket.io-parser | ≥ 4.1.0&&< 4.2.1 | 4.2.1 |
| 📦npm | socket.io-parser | all versions | 3.3.3 |
| 📦npm | socket.io-parser | ≥ 3.4.0&&< 3.4.2 | 3.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for socket.io-parser. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update socket.io-parser to 4.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qm95-pgcg-qqfq 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.
How O3 protects you
O3 pinpoints whether GHSA-qm95-pgcg-qqfq is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-qm95-pgcg-qqfq. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-qm95-pgcg-qqfq in your dependencies?
O3 detects GHSA-qm95-pgcg-qqfq across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.