CVE-2018-14731
Missing Origin Validation in parcel-bundler
An issue was discovered in HMRServer.js in Parcel parcel-bundler. Attackers are able to steal developer's code because the origin of requests is not checked by the WebSocket server, which is used for HMR (Hot Module Replacement). Anyone can receive the HMR message sent by the WebSocket server via a ws://127.0.0.1 connection (with a random TCP port number) from any origin. The random port number can be found by connecting to http://127.0.0.1 and reading the "new WebSocket" line in the source code.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in HMRServer.js in Parcel parcel-bundler. Attackers are able to steal developer's code because the origin of requests is not checked by the WebSocket server, which is used for HMR (Hot Module Replacement). Anyone can receive the HMR message sent by the WebSocket server via a ws://127.0.0.1 connection (with a random TCP port number) from any origin. The random port number can be found by connecting to http://127.0.0.1 and reading the "new WebSocket" line in the source code.
- Record
CVE-2018-14731- CVSS 3.0
- 7.5 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:P/I:N/A:N - Weakness
- CWE-200
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in HMRServer.js in Parcel parcel-bundler. Attackers are able to steal developer's code because the origin of requests is not checked by the WebSocket server, which is used for HMR (Hot Module Replacement). Anyone can receive the HMR message sent by the WebSocket server via a ws://127.0.0.1 connection (with a random TCP port number) from any origin. The random port number can be found by connecting to http://127.0.0.1 and reading the "new WebSocket" line in the source code.
- Record
CVE-2018-14731- Updated
- 2026-11-02
EUVDEUVD-2018-0484 No score
An issue was discovered in HMRServer.js in Parcel parcel-bundler. Attackers are able to steal developer's code because the origin of requests is not checked by the WebSocket server, which is used for HMR (Hot Module Replacement). Anyone can receive the HMR message sent by the WebSocket server via a ws://127.0.0.1 connection (with a random TCP port number) from any origin. The random port number can be found by connecting to http://127.0.0.1 and reading the "new WebSocket" line in the source code.
- Record
EUVD-2018-0484- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-37q6-576q-vgr7
Missing Origin Validation in parcel-bundler
Versions of parcel-bundler before 1.10.0 are missing origin validation on the websocket server. This vulnerability allows a remote attacker to steal a developer's source code because the origin of requests to the websocket server that is used for Hot Module Replacement (HMR) are not validated.
Recommendation
Update to version 1.10.0 or later.
- Record
GHSA-37q6-576q-vgr7- CVSS 3.0
- 7.5 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-200
- Updated
- 2026-11-02
OSVGHSA-37q6-576q-vgr7
Missing Origin Validation in parcel-bundler
Versions of parcel-bundler before 1.10.0 are missing origin validation on the websocket server. This vulnerability allows a remote attacker to steal a developer's source code because the origin of requests to the websocket server that is used for Hot Module Replacement (HMR) are not validated.
Recommendation
Update to version 1.10.0 or later.
- Record
GHSA-37q6-576q-vgr7- CVSS 3.0
- 7.5 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-200
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
parcel-bundlernpm |
before 1.10.0 | 1.10.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2018-14731 is a high vulnerability (CVSS 7.5) in Parceljs Parcel, published September 21, 2018. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.33%, the 83rd percentile. Fixed in parcel-bundler 1.10.0.
References
github.com/parcel-bundler/parcel/issues/1783
blog.cal1.cn/post/Sniffing%20Codes%20in%20Hot%20Module%20Reloading%20Messages
nvd.nist.gov/vuln/detail/CVE-2018-14731
npmjs.com/advisories/721