Quick answers
- Is CVE-2026-123840 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-123840 being exploited in the wild.
- How severe is CVE-2026-123840?
- Medium severity, with a CVSS score of 4.7, published 6 November 2026.
- Which products and versions are affected?
- Jetbrains IntelliJ IDEA before 2026.3.
- Is there a fix for CVE-2026-123840?
- Yes: fixed in IntelliJ IDEA 2026.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-123840 attacked?
- It is in a web application.
- Am I affected by CVE-2026-123840?
- Check whether you run Jetbrains IntelliJ IDEA at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: IntelliJ IDEA 2026.3
Technical details
An HTML injection vulnerability exists in the Remote Development editor tabs component of IntelliJ IDEA prior to version 2026.3. The vulnerability allows injection of arbitrary HTML content into editor tabs, which could be exploited through crafted remote development sessions. This is a client-side code injection affecting local user sessions in the IDE environment.
Affected products
- JetBrains IntelliJ IDEA before 2026.3
Timeline
- 2026-11-06: disclosed