CVE-2020-5207

mediumpriority · track · 30EPSS 0.008 · 55 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.76% (55th) EPSS

CVSS 5 · medium

Is it mine?

4 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · nvd · osv

EPSS · scored 2026-10-28

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.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5–7.5

v2.05mediumAV:N/AC:L/Au:N/C:N/I:P/A:Nprimary · NVD / NIST USexploitability 10 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:Nprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:Nsecondary · ENISA EU

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:Nsecondary · security-advisories@github.comexploitability 2.3 · impact 2.7

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:Nsecondary · OSV

v3.16.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-444USprimaryCWE-444US

affected products (4)

Products and version ranges known to be affected.

Ktor.io Ktor≤ < 1.3.0enisa_euvdEU
jetbrains ktor< 1.3.0nvdUScpe:2.3:a:jetbrains:ktor:*:*:*:*:*:*:*:*
Maven io.ktor:ktor-client-cio< 1.3.0osvUSpkg:maven/io.ktor/ktor-client-cio
Maven io.ktor:ktor-server-cio< 1.3.0osvUSpkg:maven/io.ktor/ktor-server-cio

advisories (1)

Vendor and ecosystem advisories describing this.

GHSA-xrr9-rh8p-433vRequest smuggling is possible when both chunked TE and content length specified2020-01-27ghsa · osvUS
### Impact Request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle alone \n as a headers separator. ### Patches https://github.com/ktorio/ktor/pull/1547 ### Workarounds None except migrating to a better proxy. ### References https://portswigger.net/web-security/request-smuggling https://tools.ietf.org/html/rfc7230#section-9.5

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd osv NVD CVE.org MITRE

published 2020-01-27modified 2026-06-17

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+549 more

references (7)

External citations — patches, advisories, analysis.

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