CVE-2020-5207 Request smuggling is possible in Ktor when both chunked TE and content length specified

What is CVE-2020-5207?

CVE-2020-5207 is a medium-severity vulnerability in Ktor.io Ktor, published on 27 Jan 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \n as a headers separator.

Weakness: CWE-444

Which versions are affected by CVE-2020-5207?

4 open source packages ship an affected version, including io.ktor:ktor-client-cio and io.ktor:ktor-server-cio. It affects 1 product.

Products include Jetbrains Ktor.

How do I fix CVE-2020-5207?

Upgrade io.ktor:ktor-client-cio to 1.3.0 or later.

Is CVE-2020-5207 being exploited?

There is no known exploitation of CVE-2020-5207 in the wild and no public exploit code.

Other vulnerabilities in Ktor.io Ktor

• CVE-2019-12736 Command injection in n/a Critical 9.8
• CVE-2022-29930 SHA1 implementation in JetBrains Ktor Native 2.0.0 was returning the same value. High 8.7
• CVE-2023-45612 XML external entity in Ktor High 8.6
• CVE-2022-48476 Path traversal in Ktor High 7.5
• CVE-2021-43203 Auth bypass in n/a High 7.5

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-xrr9-rh8p-433v.