CVE-2026-123318 In JetBrains Ktor before 3.6.1 hTTP request smuggling was possible in the CIO engine
Medium 4.8
Published
Updated
Check this codebase for CVE-2026-123318 and fix it if it is affected.
What it is: CVE-2026-123318 is a medium-severity vulnerability in JetBrains Ktor, published on 6 Nov 2026.
Exploitation: There is no known exploitation of CVE-2026-123318 in the wild and no public exploit code.
Affected product: JetBrains Ktor. 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-2026-123318/ (Markdown: https://insights.sbomify.com/CVE-2026-123318/index.md)
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-123318?
CVE-2026-123318 is a medium-severity vulnerability in JetBrains Ktor, published on 6 Nov 2026.
Official description
In JetBrains Ktor before 3.6.1 hTTP request smuggling was possible in the CIO engine
Weakness: CWE-444
Which versions are affected by CVE-2026-123318?
How do I fix CVE-2026-123318?
No fix has been published for CVE-2026-123318 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-123318 being exploited?
There is no known exploitation of CVE-2026-123318 in the wild and no public exploit code.
Sources
Also known as GHSA-6mmc-8ffm-69rw.