CVE-2026-123309 In JetBrains IntelliJ IDEA before 2026.3, 2026.2.4 stored XSS was possible on the built-in web server via Markdown preview
Medium 6.1
Published
Updated
Check this codebase for CVE-2026-123309 and fix it if it is affected.
What it is: CVE-2026-123309 is a medium-severity vulnerability in JetBrains IntelliJ IDEA, published on 6 Nov 2026.
Exploitation: There is no known exploitation of CVE-2026-123309 in the wild and no public exploit code.
Affected product: JetBrains IntelliJ IDEA. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-123309/ (Markdown: https://insights.sbomify.com/CVE-2026-123309/index.md)
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-123309?
CVE-2026-123309 is a medium-severity vulnerability in JetBrains IntelliJ IDEA, published on 6 Nov 2026.
Official description
In JetBrains IntelliJ IDEA before 2026.3, 2026.2.4 stored XSS was possible on the built-in web server via Markdown preview
Weakness: CWE-79
Which versions are affected by CVE-2026-123309?
It affects 1 product.
Products include JetBrains IntelliJ IDEA.
How do I fix CVE-2026-123309?
No fix has been published for CVE-2026-123309 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-123309 being exploited?
There is no known exploitation of CVE-2026-123309 in the wild and no public exploit code.
Other vulnerabilities in JetBrains IntelliJ IDEA
- CVE-2026-64812 In JetBrains IntelliJ IDEA before 2026.2 unauthorized input injection was possible in a Remote Development session
- CVE-2026-64813 In JetBrains IntelliJ IDEA before 2026.2 unauthorized settings modification was possible in a Remote Development session
- CVE-2020-11690 In JetBrains IntelliJ IDEA before 2020.1, the license server could be resolved to an untrusted host in some cases.
- CVE-2019-10104 In several JetBrains IntelliJ IDEA Ultimate versions, an Application Server run configuration (for Tomcat, Jetty, Resin, or CloudBees) with
- CVE-2019-9186 In several JetBrains IntelliJ IDEA versions, a Spring Boot run configuration with the default setting allowed remote attackers to execute co
Sources
Also known as GHSA-4rqw-p72p-2m5j.