Quick answers
- Is CVE-2026-123318 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-123318 being exploited in the wild.
- How severe is CVE-2026-123318?
- Medium severity, with a CVSS score of 4.8, published 6 November 2026.
- Which products and versions are affected?
- Jetbrains Ktor before 3.6.1.
- Is there a fix for CVE-2026-123318?
- Yes: fixed in 3.6.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-123318 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-123318?
- Check whether you run Jetbrains Ktor 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: 3.6.1
Technical details
HTTP request smuggling vulnerability exists in the CIO (Coroutine I/O) engine of JetBrains Ktor versions before 3.6.1. The vulnerability allows an attacker to craft ambiguous HTTP requests that are interpreted differently by the proxy/WAF and the backend server, leading to request smuggling. This requires network access and no authentication.
Affected products
- JetBrains Ktor before 3.6.1
Timeline
- 2026-11-06: disclosed