← Vulnerability feed

Vulnerability record · CVE-2021-43203 · published 9 November 2021

CVE-2021-43203: Jetbrains ktor improper authentication vulnerability

Jetbrains · Ktor

In JetBrains Ktor before 1.6.4, nonce verification during the OAuth2 authentication process is implemented improperly.

7.5 CVSS 3.1 High EPSS 0.86% · top 43.0% CWE-287 · Improper authentication
7.5CVSS 3.1 base score, v2 5.0
0.86%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

In JetBrains Ktor before 1.6.4, nonce verification during the OAuth2 authentication process is implemented improperly.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://blog.jetbrains.com/blog/2021/11/08/jetbrains-security-bulletin-q3-2021/ Vendor Advisory
https://blog.jetbrains.com/blog/2021/11/08/jetbrains-security-bulletin-q3-2021/ Vendor Advisory

Track CVE-2021-43203 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2023-45612Jetbrains ktor xml external entity (xxe) vulnerabilityIn JetBrains Ktor before 2.3.5 default configuration of ContentNegotiation with XML format was vulnerable to XXEEPSS 0.60%9.8CVE-2019-12736Jetbrains ktor command injection vulnerabilityJetBrains Ktor framework before 1.2.0-rc does not sanitize the username provided by the user for the LDAP protocol, leading to command injection.EPSS 2.2%9.1CVE-2023-45613Jetbrains ktor improper certificate validation vulnerabilityIn JetBrains Ktor before 2.3.5 server certificates were not verifiedEPSS 0.30%8.1CVE-2019-10102Jetbrains kotlin cleartext transmission vulnerabilityJetBrains Ktor framework (created using the Kotlin IDE template) versions before 1.1.0 were resolving artifacts using an http connection during the b…EPSS 0.82%7.5CVE-2022-48476Jetbrains ktor path traversal vulnerabilityIn JetBrains Ktor before 2.3.0 path traversal in the `resolveResource` method was possibleEPSS 0.75%7.5CVE-2020-5207Jetbrains ktor http request smuggling vulnerabilityIn 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 …EPSS 0.76%6.5CVE-2022-38180Jetbrains ktor improper authentication vulnerabilityIn JetBrains Ktor before 2.1.0 the wrong authentication provider could be selected in some casesEPSS 0.72%6.5CVE-2020-26129Jetbrains ktor http request smuggling vulnerabilityIn JetBrains Ktor before 1.4.1, HTTP request smuggling was possible.EPSS 0.77%

Source: NIST National Vulnerability Database (record CVE-2021-43203), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.